Answer
$\dfrac{9}{2} \pi$
Work Step by Step
Here, $A=(2) \int_{0}^{\pi} (\dfrac{1}{2}) r^2 d\theta$
Then, $A=2 \int_{0}^{\pi} (2-\cos \theta)^2$
This implies that
$A=\int_{0}^{\pi} [4+\cos^2 \theta-4 (\cos \theta) ]d\theta=\dfrac{9}{2} \pi$