Question 1193178
A rectangle is inscribed in a circle of radius r.
 If the rectangle has a length of 3x, write the area of the rectangle as a function of both x and r 
:
let s = the short side of the rectangle
then
A = 3x * s
find s as a function of r and x
The diagonal of the rectangle = 2r
Using pythag
s^2 + (3x)^2 = (2r)^2
s^2 = (2r)^2 - (3x)^2
s = {{{sqrt((2r)^2 - (3x)^2)}}}
:
A = {{{3x*sqrt((2r)^2 - (3x)^2)}}}
or
{{{3x*sqrt((4r^2) - (9x^2))}}}