Plane and solid analytic geometry; an elementary textbook (1905)
Ashton, Charles H. (Charles Hamilton), 1866- · New York, C. Scribner's Sons · leaf 152
con-structed. If the whole or part of the sides of a room is a surface formedby revolving an ellipse about its major axis, all waves of sound, light, orheat starting from one focus and striking this surface will be reflected tothe other focus. 2. In an liyjyerhola the tangent and normal at any… … Fig. 72. Since the direction of a curve at any point is along thetangent at that point, two curves intersect orthogonally,if their tangents at the point of intersection are perpen-dicular to each other. Tliis is evidently the case here,since the tangent to the ellipse bisects the exterior angle 136…
Geometry, Analytic
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