Question

A rectangle with one side 4cm is inscribed in a circle of radius 2.5cm the area of rectangle is

Answer 1

Since the radius is 2.5, the diameter is 5.
A diagonal for the rectangle is equal to this diameter.
We have a triangle with side lengths of 5 and 4.
5 is the hypotenuse. Set x = the length of the 
other side of the triangle.


So 

add -16 to each side

x = 3
We have side lengths of 3 and 4 so
the area = 3*4 = 12