Trigonometryhard · Past Paper
If x = r sin A cos B, y = r sin A sin B, z = r cos A, then x^2 + y^2 + z^2 is:
Ar
Br^2
Cr^3
D1
✓ Correct Answer: B — r^2
x^2 + y^2 = r^2 sin^2 A (cos^2 B + sin^2 B) = r^2 sin^2 A. Then r^2 sin^2 A + r^2 cos^2 A = r^2.
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