Q. PQRS is a rectangle in which PQ = 20 cm and QR = 10 cm. A semicircle is drawn with centre at O and radius 10$\sqrt{2}$ cm. It passes through A and B as shown in figure. Find the area of the shaded region.

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See the place where I'm finding theta u can also find it by *angle sum property of the triangle* since it is an isosceles triangle...
I checked it later