Hello,Originally Posted by Yumi
I've attached a diagram to demonstrate what I calculated.
Let r be the radius of the circle.
Let angle(CBA)= alpha. Then angle(DCB)=180°-alpha.
The triangle (BMO) is a right triangle. The triangle (OSC) is a right triangle.
Now use the tangens:
So you get:
Solve for r and you'll get r = 6.
That means the height of the trapezoid is 12. Therefore the area is 156 (square units).