# How do I find the area of a circle inside a square?

In the figure above, the circle with center $O$ is inscribed in square $ABCD$. What is the area of the shaded portion of the circle?

(A) $\pi/4$

(B) $\pi/2$

(C) $\pi$

(D) $3\pi/2$

(E) $2\pi$

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Hint: The circle has radius $1$. By symmetry (join the centre of the circle to the other corners of the square) the shaded part of the circle is one-quarter of the whole circle.