This area of the circle is and the area of triangle is .
What is the measure of in degrees?
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Since the circle's area equals π , the radius must be 1. Now let's call the angle FOG 2 α . The area of the blue triangle can be written as function of α . The height of the triangle equals c o s ( α ) and the base equals 2 s i n ( α ) . Now the area of the blue triangle is: 2 1 ⋅ 2 s i n ( α ) c o s ( α ) = 2 1 ⋅ s i n ( 2 α ) = 0 . 2 5 . So s i n ( 2 α ) = 0 . 5 and 2 α = 3 0 . This leads to ∠ A O F = 9 0 − 3 0 = 6 0 .