Question 1018157
The inscribed triangle is a right triangle, and the longest side, its hypotenuse, is a diameter of the circle, 52 cm.


u, the unknown leg:
{{{u^2+20^2=52^2}}} according to Pythagorean Theorem Formula;
{{{u^2=52^2-400}}}
{{{u^2=2304}}}
{{{u^2=576*4=288*2*4=144*2*2*4}}}
{{{u^2=12*12*4*4}}}
{{{highlight(u=48)}}}


The 90-degree angle of the triangle is between u=48, and 20 cm leg.


If you want the area of the inscribed triangle by itself, then  {{{highlight((1/2)*48*20=highlight(480))}}}.