Section 1.4

Second-Order Curves in Simplest Form

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Problem 164

Find the equation of the parabola passing through the point (6,9)(6,9), with vertex at the origin and symmetric with respect to the axis OyOy.

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Problem 165

The axis OxOx is the axis of symmetry of a parabola with vertex at the origin. Find the equation of this parabola, given that it passes through the point (2,2)(2,2).

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Problem 166

The parabolic mirror of the telescope reflector at Simeiz had a focal length of 5,45{,}4 m and a diameter of 1,021{,}02 m. Find the depth of the parabolic concavity of the mirror.

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Problem 167

The mirror of an automobile headlight has, in cross-section, the shape of a parabola. The diameter of the mirror is 2020 cm, its depth is 1010 cm. Find the position of the focus of the mirror.

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Problem 168

Prove that all parabolas y2=2pxy^{2}=2px are geometrically similar.

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Problem 169

On the parabola y2=24xy^{2}=24x a point is taken at a distance of 14 units from the focus. Determine its distance from the vertex.

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Problem 170

Prove that the product of the ordinates of the endpoints of any chord passing through the focus of the parabola y2=2pxy^{2}=2px is a constant quantity.

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Problem 171

On the parabola y2=2pxy^{2}=2px find a point such that its distances from the focus and from the vertex are in the ratio 7:87:8.

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Problem 172

The parabola y2=4−4xy^{2}=4-4x and the line x+y=1x+y=1 are given. Through one of their points of intersection, draw another parabola with the same axis and focus.

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Problem 173

Set up the equation of the parabola with axis of symmetry OxOx, passing through the points (a,0)(a,0), (0,b)(0,b). For what relation between aa and bb will the focus of the parabola be at the origin?

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Problem 174

The parabolas y2=4x+8y^{2}=4x+8 and 4x+y2−4y−8=04x+y^{2}-4y-8=0 are given. Find the equation of their common chord and its point of intersection with the line joining the foci.

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Problem 175

Three points (−5,2)(-5,2), (1,−4)(1,-4) and (5,12)(5,12) are given, lying on a parabola whose axis is parallel to the axis OyOy. Find the vertex, focus, and directrix of this parabola.

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Problem 176

Through three points (−2,1)(-2,1), (−1,0)(-1,0) and (6,1)(6,1), draw a circle and a parabola with axis parallel to the axis OyOy. Determine the distance from the center of the circle to the vertex of the parabola.

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Problem 177

Prove that the equation yy1=p(x+x1)yy_{1}=p(x+x_{1}) represents the tangent to the parabola y2=2pxy^{2}=2px at the point (x1,y1)(x_{1},y_{1}).

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Problem 178

The parabolas y2+4x=0y^{2}+4x=0 and y2=16x+80y^{2}=16x+80 are given. Verify that they are confocal and that the tangents at the points of intersection are mutually perpendicular.

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Problem 179

Three points (−3,2)(-3,2), (−1,1)(-1,1) and (3,5)(3,5) are given; draw through them a parabola with axis parallel to the axis OyOy, and a circle, and find the angles at which they intersect.

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Problem 180

Prove that the tangent to the parabola y2=2pxy^{2}=2px having slope mm is represented by the equation y=mx+p2my = mx+\frac{p}{2m}.

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Problem 181

Find the tangent to the parabola 4y=x24y=x^{2} at the point (2,1)(2,1).

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Problem 182

Through the point (0,−4)(0,-4) draw a tangent to the parabola 4y=x24y=x^{2}.

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Problem 183

Through the point (−4,−1)(-4,-1) draw a tangent to the parabola y2=2xy^{2}=2x.

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Problem 184

Prove that the tangents drawn at the endpoints of a chord of a parabola passing through the focus are mutually perpendicular.

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Problem 185

The parabola y2=2pxy^{2}=2px is given. Find the angle between the tangents to it drawn from the point (−p,p)(-p,p).

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Problem 186

Find the distance from the focus of the parabola y2=2pxy^{2}=2px to a tangent to it whose angle with the axis equals α\alpha.

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Problem 187

Find the locus of the feet of the perpendiculars dropped from the focus of a parabola onto its tangents.

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Problem 188

The parabola 4y+x2−4x−12=04y+x^{2}-4x-12=0 and the line y−2x=0y-2x=0 are given. Draw the tangent parallel to the given line.

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Problem 189

Find the common tangents to the parabola y2=8xy^{2}=8x and the circle x2+y2=2x^{2}+y^{2}=2.

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Problem 190

Two parabolas are given: y2=2pxy^{2}=2px and y2=2p(x+a)y^{2}=2p(x+a). Prove that the segments of the tangent to the first parabola lying inside the second are bisected by the point of tangency.

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Problem 191

Find the locus of points from which the parabola is seen at a right angle.

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Problem 192

The ordinates of the circle x2+y2=36x^{2}+y^{2}=36 are decreased by half. Find the equation of the resulting curve.

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Problem 193

Find the semi-axes of the ellipse 3x2+5y2−30=03x^{2}+5y^{2}-30=0.

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Problem 194

Find the equation of the ellipse passing through the points (1,4)(1,4) and (7,2)(7,2) and symmetric with respect to the axes OxOx and OyOy.

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Problem 195

Prove that ellipses with the same eccentricity ee are geometrically similar, i.e., can be brought into coincidence with each other by suitably enlarging one of them.

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Problem 196

The meridian of the terrestrial globe is an ellipse whose flattening, i.e., a−ba\frac{a-b}{a}, equals 1298\frac{1}{298}. Find its eccentricity.

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Problem 197

The orbit of the terrestrial globe is an ellipse with semi-axis a=150⋅106a=150 \cdot 10^{6} km and eccentricity e=0,017e=0{,}017. Knowing that the Sun is at the focus of this ellipse, find by how much the shortest distance from the Earth to the Sun (January 4) is shorter than the longest (July 3).

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Problem 198

Two points are given, lying on an ellipse whose axes are the coordinate axes — (3;2,4)(3;2{,}4) and (4;1,8)(4;1{,}8). Find this ellipse and the projections of the foci onto the chord joining the given points.

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Problem 199

An ellipse and a parabola are given: y2=18x−0,36x2y^{2}=18x-0{,}36x^{2}, y2=18xy^{2}=18x. Find the distance from the focus of the parabola to the nearest focus of the ellipse.

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Problem 200

Find the eccentricity of an equilateral (rectangular) hyperbola.

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Problem 201

The directrices of a hyperbola divide the distance between the foci into three equal parts. Find its eccentricity.

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Problem 202

The foci of an ellipse divide the distance between the directrices into three equal parts. Find its eccentricity.

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Problem 203

What will the equation of the equilateral hyperbola x2−y2=a2x^{2}-y^{2}=a^{2} become if the axes are rotated through an angle α=−45∘\alpha =-45^{\circ }?

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Problem 204

The distance between the foci of an ellipse equals 2, and the distance between the directrices equals 10. Find the semi-axes.

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Problem 205

The eccentricity of a hyperbola equals 2. Find the angle between the asymptotes.

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Problem 206

The minor axis of an ellipse is seen from the focus at a right angle. Find the eccentricity.

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Problem 207

The hyperbola x2−y2=8x^{2}-y^{2}=8 is given. Find the confocal ellipse passing through the point (4,6)(4,6).

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Problem 208

The ellipse b2x2+a2y2=a2b2b^{2}x^{2}+a^{2}y^{2}=a^{2}b^{2} is given. Write the equation of the confocal equilateral hyperbola.

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Problem 209

Find the general equation of the ellipses and hyperbolas with foci at the points (±c,0)(\pm c,0).

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Problem 210

The ellipse x28+y25=1\frac{x^{2}}{8}+\frac{y^{2}}{5}=1 is given. Find the equation of the hyperbola having its foci at the vertices of the given ellipse, and its vertices at the foci.

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Problem 211

The ellipse x233+y28=1\frac{x^{2}}{33}+\frac{y^{2}}{8}=1 is given. Find the hyperbola confocal with it, having eccentricity equal to 1,251{,}25.

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Problem 212

Find the ellipse and the hyperbola passing through the point (6,4)(6,4) and confocal with the hyperbola

x2−y2+8=0. x^{2}-y^{2}+8=0.
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Problem 213

The coordinate axes serve as the axes of a hyperbola passing through the point (6,5)(6,5) and having eccentricity equal to 1,51{,}5. Set up its equation.

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Problem 214

Find the points at which the hyperbola x264−y236=1\frac{x^{2}}{64}-\frac{y^{2}}{36}=1 is met by the lines parallel to the asymptotes and passing through the right focus.

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Problem 215

Find the distance from the focus of the hyperbola b2x2−a2y2=a2b2b^{2}x^{2}-a^{2}y^{2}=a^{2}b^{2} to an asymptote.

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Problem 216

The polar equation of a second-order curve is r(5+3cos⁡φ)=16r(5+3\cos \varphi )=16. Find its equation with respect to its axes of symmetry.

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Problem 217

The same, for the curve r(4+5cos⁡φ)=9r(4+5\cos \varphi )=9.

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Problem 218

Prove the equality

1ρ1+1ρ2+…+1ρn=np, \frac{1}{\rho _{1}}+\frac{1}{\rho _{2}}+\ldots +\frac{1}{\rho _{n}} = \frac{n}{p},

where ρ1\rho_{1}, ρ2\rho_{2}, , ρn\rho_{n} are the radius vectors drawn from the focus of a parabola at angles 2πn\frac{2\pi }{n} to one another.

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Problem 219

Prove the equality

1r12+1r22=1a12+1b22, \frac{1}{r_{1}^{2}}+\frac{1}{r_{2}^{2}} = \frac{1}{a_{1}^{2}}+\frac{1}{b_{2}^{2}},

where r1r_{1} and r2r_{2} are mutually perpendicular radius vectors drawn from the center of an ellipse.

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Problem 220

Prove the equality

1r12+1r22+…+1rn2=n2(1a2+1b2), \frac{1}{r_{1}^{2}}+\frac{1}{r_{2}^{2}}+\ldots +\frac{1}{r_{n}^{2}} = \frac{n}{2}\left(\frac{1}{a^{2}}+\frac{1}{b^{2}}\right),

where r1r_{1}, r2r_{2}, , rnr_{n} are radius vectors from the center of an ellipse, making angles 2πn\frac{2\pi }{n} with one another.

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Problem 221

Find the equations of the diameters of the ellipse x2+6y2=2x^{2}+6y^{2}=2 whose length equals 2.

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Problem 222

Prove that under projection, mutually perpendicular diameters of a circle pass into conjugate diameters of an ellipse.

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Problem 223

Using the theorem that the area of a projection equals the area of the figure itself multiplied by the cosine of the angle between the plane of the figure and the plane of projection, prove Apollonius's theorem: a1b1sin⁡ω=aba_{1}b_{1}\sin \omega = ab, where a1a_{1} and b1b_{1} are the lengths of conjugate semi-diameters of an ellipse, and ω\omega is the angle between them.

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Problem 224

Starting from the result of problem 222, prove another theorem of Apollonius, according to which a12+b12=a2+b2a_{1}^{2}+b_{1}^{2}=a^{2}+b^{2}.

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Problem 225

Find the angle between the equal conjugate diameters of the ellipse x2+3y2=6x^{2}+3y^{2}=6.

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Problem 226

Find the lengths of the conjugate diameters of the hyperbola x2−y2=1x^{2}-y^{2}=1 between which the angle equals 45∘45^{\circ }.

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Problem 227

Find the lengths of the conjugate diameters of the ellipse x2+15y2=5x^{2}+15y^{2}=5 between which the angle equals 150∘150^{\circ }.

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Problem 228

The angle between conjugate diameters of an ellipse equals 120∘120^{\circ }. One of them is twice the other. Find the eccentricity.

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Problem 229

Find the lengths of the conjugate diameters of the ellipse x25+3y2=1\frac{x^{2}}{5}+3y^{2}=1 making an angle of 150∘150^{\circ }.

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Problem 230

The lengths of the conjugate diameters of the ellipse 8x2+17y2=1368x^{2}+17y^{2}=136 are in the ratio 4:34:3. Find the equations of these diameters.

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Problem 231

The sum of the lengths of conjugate diameters is 6, the angle between them is 150, and the eccentricity is e=35e=\frac{3}{5}. Find the axes of the ellipse.

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Problem 232

Find the lengths of the conjugate diameters of the ellipse 3x2+5y2=153x^{2}+5y^{2}=15 making the largest angle.

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Problem 233

Find the angle between the conjugate diameters of a hyperbola, given the ratio mm of their lengths and the eccentricity ee.

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Problem 234

Find the angle between the asymptotes of a hyperbola, given that its conjugate diameters form an angle of 45∘45^{\circ } and are in the ratio 2 to 3.

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Problem 235

Find the lengths of the conjugate diameters of the hyperbola 9x2−16y2=1449x^{2}-16y^{2}=144 whose sum is to the sum of the axes as 5 to 2.

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Problem 236

Prove that the equation Axx1+Byy1+C=0Axx_{1}+Byy_{1}+C=0 represents the tangent to the curve Ax2+By2+C=0Ax^{2}+By^{2}+C=0 at the point (x1,y1)(x_{1},y_{1}).

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Problem 237

The ellipse 4x2+y2=84x^{2}+y^{2}=8 and the line y−2x=0y-2x=0 are given. Draw the tangents to the ellipse parallel to this line, and find the distance between the tangents.

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Problem 238

Through the point (2,−1)(2,-1) draw a tangent to the ellipse x2+9y2=9x^{2}+9y^{2}=9.

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Problem 239

Through the point (3,−6)(3,-6) draw a tangent to the hyperbola 4x2−9y2=364x^{2}-9y^{2}=36.

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Problem 240

Through the point (1,−2)(1,-2) draw a tangent to the hyperbola x2−y2=1x^{2}-y^{2}=1.

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Problem 241

Draw, parallel to the line 2x−3y=02x-3y=0, tangents to the ellipse x2+4y2=4x^{2}+4y^{2}=4.

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Problem 242

Parallel to the line 10x+3y=010x+3y=0, draw tangents to the hyperbola 4x2−y2=44x^{2}-y^{2}=4.

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Problem 243

Find the tangents to the hyperbola 4x210−y26=1\frac{4x^{2}}{10}-\frac{y^{2}}{6}=1 at its points of intersection with the line 3x=5y3x=5y, and the distance between these tangents.

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Problem 244

Given: the ellipse x245+y236=1\frac{x^{2}}{45}+\frac{y^{2}}{36}=1 and the hyperbola x25−y24=1\frac{x^{2}}{5}-\frac{y^{2}}{4}=1. Verify that the tangents to them at the points of intersection are mutually perpendicular.

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Problem 245

Two ellipses are given: x215+y29=1\frac{x^{2}}{15}+\frac{y^{2}}{9}=1 and x219+y23=1\frac{x^{2}}{19}+\frac{y^{2}}{3}=1. Find the tangents to the first ellipse passing through the foci of the second.

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Problem 246

Find the tangents to the hyperbola x215+y221=1\frac{x^{2}}{15}+\frac{y^{2}}{21}=1 passing through a focus of the conjugate hyperbola.

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Problem 247

Find the angle between the tangents to the hyperbola x29−y24=1\frac{x^{2}}{9}-\frac{y^{2}}{4}=1 drawn from the point (1,2)(1,2).

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Problem 248

Prove that the tangent to the ellipse x2a2+y2b2=1\frac{x^{2}}{a^{2}}+\frac{y^{2}}{b^{2}}=1 having slope mm is represented by the equation

y=mx±a2m2+b2. y = mx \pm \sqrt{a^{2}m^{2}+b^{2}}.
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Problem 249

Prove that the tangent to the hyperbola x2a2+y2b2=σ\frac{x^{2}}{a^{2}}+\frac{y^{2}}{b^{2}}=\sigma having slope mm is represented by the equation

y=mx±σ(a2m2−b2). y = mx \pm \sqrt{\sigma (a^{2}m^{2}-b^{2})}.
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Problem 250

Prove that the chords joining the points of intersection of the circle x2+y2=a2+b2x^{2}+y^{2}=a^{2}+b^{2} with the coordinate axes are tangent to the ellipse x2a2+y2b2=1\frac{x^{2}}{a^{2}}+\frac{y^{2}}{b^{2}}=1.

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Problem 251

Show that the ellipses x2a2+y2b2=1\frac{x^{2}}{a^{2}}+\frac{y^{2}}{b^{2}}=1 are tangent to the lines ±x±y=c\pm x \pm y = c, if a2+b2=c2a^{2}+b^{2}=c^{2}.

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Problem 252

Prove that the locus of points from which the ellipse x2a2+y2b2=1\frac{x^{2}}{a^{2}}+\frac{y^{2}}{b^{2}}=1 is seen at a right angle is the circle x2+y2=a2+b2x^{2}+y^{2}=a^{2}+b^{2}.

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Problem 253

Show that for the hyperbola x2a2−y2b2=1\frac{x^{2}}{a^{2}}-\frac{y^{2}}{b^{2}}=1, the product of the distances of the foci from a tangent equals bb.

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