, what is ?
Recall that the measure of each inscribed angle is half the arc it intercepts.
What is the sum of interior angles for triangles?
and , what is the area of ?
is , use the Pythagorean Theorem to solve for the .
Then from there, substitute the information you found in the equation for the area of a circle.
If the radius of
is and if , what is ?
Recall your trigonometric ratios.