Subsection 6.4

Coordinate system transformation (6.93-6.97)

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Problem 6.93

Given two coordinate systems O,e1,e2,e3O, \mathbf{e}_{1}, \mathbf{e}_{2}, \mathbf{e}_{3} and O′,e1′O^{\prime }, \mathbf{e}_{1}^{\prime }, e2′,e3′\mathbf{e}_{2}^{\prime }, \mathbf{e}_{3}^{\prime }. The origin of the second coordinate system has coordinates a10,a20,a30a_{10}, a_{20}, a_{30} in the first system, and the basis vectors of the second system have coordinates (a11,a21,a31)\left(a_{11}, a_{21}, a_{31}\right), (a12,a22,a32),(a13,a23,a33)\left(a_{12}, a_{22}, a_{32}\right), \left(a_{13}, a_{23}, a_{33}\right) respectively in the basis of the first system. In the first coordinate system a plane is given by the equation Ax+By+Cz+D=0Ax + By + Cz + D = 0. Find the equation of this plane in the second system.

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Problem 6.94

In space, four points A(1,2,1)A(1, 2, 1), B(−1,3,0),C(2,5,3),D(−2,3,4)B(- 1, 3, 0), C(2, 5, 3), D(- 2, 3, 4) and a plane 2x+y−3z+2=02x + y - 3z + 2 = 0 are given. Find the equation of this plane in the new coordinate system A,AB→,AC→,AD→A, \overrightarrow {AB}, \overrightarrow {AC}, \overrightarrow {AD}.

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Problem 6.95

The planes x−2y+3z−6=0,2x+y−z=0,4x+z−5=0x - 2y + 3z - 6 = 0, 2x + y - z = 0, 4x + z - 5 = 0 are respectively the planes O′y′z′,O′z′x′O^{\prime } y^{\prime } z^{\prime }, O^{\prime } z^{\prime } x^{\prime }, O′x′y′O^{\prime } x^{\prime } y^{\prime } of a new coordinate system, and the point A(2,0,1)A(2, 0, 1) has coordinates 1,1,11, 1, 1 in the new system.

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(1)

Find the coordinates of a point in the original coordinate system, if its coordinates x′,y′,z′x^{\prime }, y^{\prime }, z^{\prime } in the new system are known.

(2)

Find, in the new coordinate system, the canonical equations of the line which in the original system is given by the equations x−11=y+1−4=z−2−1\frac{x - 1}{1} = \frac{y + 1}{ - 4} = \frac{z - 2}{ - 1}.

Problem 6.96

In a rectangular coordinate system O,e1,e2,e3O, \mathbf{e}_{1}, \mathbf{e}_{2}, \mathbf{e}_{3} a plane is given by the equation 3x+5y+2z+2=03x + 5y + \sqrt{2} z + \sqrt{2} = 0. The origin of the new rectangular coordinate system is at the point O′(1,1,−1)O^{\prime }(1, 1, - 1), the basis vector e3′\mathbf{e}_{3}^{\prime } is opposite to the vector e3\mathbf{e}_{3}, and the basis vectors e1′\mathbf{e}_{1}^{\prime } and e2′\mathbf{e}_{2}^{\prime } are obtained from the vectors e1\mathbf{e}_{1} and e2\mathbf{e}_{2} respectively by a rotation, in the plane containing e1\mathbf{e}_{1} and e2\mathbf{e}_{2}, through an angle of 45∘45^{\circ } in the direction of the shortest rotation from e1\mathbf{e}_{1} to e2\mathbf{e}_{2}.

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(1)

Find the coordinates of a point in the original coordinate system, if its coordinates x′,y′,z′x^{\prime }, y^{\prime }, z^{\prime } in the new system are known.

(2)

Find the equation of the given plane in the new coordinate system.

Problem 6.97

Three planes, given in a rectangular coordinate system by the equations x+2y−2z+3=0,2x+y+2z=0x + 2y - 2z + 3 = 0, 2x + y + 2z = 0, 2x−2y−z+3=02x - 2y - z + 3 = 0 (verify that they are pairwise perpendicular), are respectively the planes O′y′z′,O′z′x′O^{\prime } y^{\prime } z^{\prime }, O^{\prime } z^{\prime } x^{\prime }, O′x′y′O^{\prime } x^{\prime } y^{\prime } of a new rectangular coordinate system, and the point A(−1,0,0)A(- 1, 0, 0) has positive coordinates in the new system.

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(1)

Find the coordinates of a point in the original coordinate system, if its coordinates x′,y′,z′x^{\prime }, y^{\prime }, z^{\prime } in the new system are known.

(2)

Find, in the new coordinate system, the canonical equations of the lines given in the original system by the equations x−12=y−11=z−31\frac{x - 1}{2} = \frac{y - 1}{1} = \frac{z - 3}{1} and x=y=zx = y = z. Compute, in both coordinate systems, the angle and the distance between these lines; verify that the results agree.