help with 2 questions

[almostdonewithschooling]

please help out  with these 2 questions  ty

[AlphaZero]

please help out  with these 2 questions  ty

Question 7a
The area of a circle of radius \(r\) is \(\pi r^2\).
Since \(OA\) is the radius,  \(\text{area}=\pi\!\times\!2^2=4\pi \text{ cm}^2\)

Question 7b
The shaded region is exactly one-sixth of the entire circle, so it has \(\text{area}=\dfrac{1}{6}\times 4\pi=\dfrac{2\pi}{3}\ \text{cm}^2\).
Question 15
From the Pythagorean theorem,  \(AC=\sqrt{2^2+2^2}=2\sqrt{2}\ \text{cm}\).
Then,  \(DE=CE-CD=2\sqrt{2}-2\ \text{cm}\).