Section 16.3

Parametric Form of Integrals, Transversality

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Problem 5998

Find the maximum of the integral

I=∫(x1,y1)(x2,y2)(12(xy′−yx′)−Rx′2+y′2) dτ,R>0. I = \int _{(x_{1},y_{1})}^{(x_{2},y_{2})} \left(\frac{1}{2}(xy'-yx') - R\sqrt{x'^{2}+y'^{2}}\right) \, d\tau , \quad R > 0.
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Problem 5999

Find the geodesic lines on the surface of revolution r2=2f(z)r^{2} = 2f(z) (rr, φ\varphi, zz are cylindrical coordinates). Determine for which arcs M1M2M_{1}M_{2} the integral ∫M1M2ds\int_{M_{1}}^{M_{2}} ds is indeed a minimum.

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Problem 6000

Find the geodesic lines of the circular cylinder r=Rr = R.

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Problem 6001

Find the geodesic lines of the cone r=ztg⁡αr = z \operatorname {tg} \alpha.

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Problem 6002

Investigate the geodesic lines on a sphere of radius RR, find the extremals, investigate Jacobi's condition, and determine the character of the minimum of the integral ∫ds\int ds.

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Problem 6003

Find the geodesic lines on the paraboloid of revolution 2z=r22z = r^{2}. Under what condition will the geodesic line between two points on the same meridian be the shortest distance?

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Problem 6004

For the oblate ellipsoid of revolution

x2+z2a2+y2b2=1;a>b \frac{x^{2}+z^{2}}{a^{2}} + \frac{y^{2}}{b^{2}} = 1; \quad a > b

the equator (y=0y=0, x2+z2=a2x^{2}+z^{2}=a^{2}) is a geodesic line. Show that the critical point A′A' conjugate to the point AA on this line is at a distance πb\pi b from AA.

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Problem 6005

We have two circles of radius rr with centers at the points M1(−a,b)M_{1}(-a,b) and M2(a,b)M_{2}(a,b). A curve lies in the upper half-plane, ending on the given circles, and when rotated about OXOX gives a surface of the smallest area. At what points and at what angle does it intersect the circles?

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Problem 6006

Write down the transversality condition for the integral

I=∫M1M2(12(xy′−x′y)−Rx′2+y′2) dτ. I = \int _{M_{1}}^{M_{2}} \left(\frac{1}{2}(xy'-x'y) - R\sqrt{x'^{2}+y'^{2}}\right) \, d\tau .
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Problem 6007

For which integrals of the form ∫F(x,y,y′) dx\int F(x,y,y') \, dx does transversality reduce to orthogonality?

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Problem 6008

Find all integrals ∫f(x,y,y′) dx\int f(x,y,y') \, dx for which the transversals intersect the extremals at an angle of 45°45°.

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Problem 6009

Among the lines joining the point O(0,0)O(0,0) with the curve y3=2−xy^{3} = 2-x, find the one that gives the minimum of the integral

I=12∫(0,0)(x1,y1)(y′2−y2) dx. I = \frac{1}{2} \int _{(0,0)}^{(x_{1},y_{1})} (y'^{2}-y^{2}) \, dx.
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Problem 6010

In the vertical plane XOYXOY with the axis OYOY directed downward, find the curve, moving along which a heavy material point will arrive in the shortest time from the point OO to a given line y=(x−c)tg⁡βy = (x-c)\operatorname {tg}\beta; 0<β<π0 < \beta < \pi. Here the initial velocity is zero.

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