Let P(x,a) and Q(-x,a) be two points on the upper half of the ellipse
\frac{x^2}{100}+\frac{(y-5)^2}{25}=1
centered at (0,5). A triangle RST is formed by using the tangent lines to the ellipse at Q and P.
Show that the area of the triangle is
A(x)=-f'(x)[x-\frac{f(x)}{f'(x)}]^2...