Similarly, if we pass the plane BCD through P parallel to the YOZ-plane, its equation is
and for the section means the same as . Hence
- slope of section DI at P.
Illustrative Example 1. Given the ellipsoid ; find the slope of the section of the ellipsoid made (a) by the plane at the point where and is positive; (b) by the plane at the point where and is positive.
Solution. Considering as constant, = 0, or When is a constant = 0, or
- (a) When and . ∴ Ans.
- (b) When and . ∴ Ans.