Circle, Triangle, and Arc

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What is the area of the circle above with center O?

(1) The area of is 50.

(2) The length of arc ACB is .

Review: Circle, Triangle, and Arc




Explanation

We have both a circle and what appears to be a 45-45-90 triangle here, two geometric entities that tend to create situations of data sufficiency. On to the statements, separately first.

Statement (1) tells us the area of the triangle. Each of the non-hypotenuse sides is a radius of the circle so and , so we can find the area of the circle. Sufficient.

Statement (2) tells us the length of the arc ACB, which includes the three-quarters of angle measure not encompasses by the right angle of the triangle. Likewise, this arc will comprise three-quarters of the circle's circumference, so we can write . Again, we can find , so we can determine the area of the circle. Sufficient.

The correct answer is (D).


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