The given figure shows a rectangle ABCD inscribed in a circle as shown alongside.

If AB = 28 cm and BC = 21 cm, find the area of the shaded portion of the given figure.

ABCD is a rectangle. So, ∠ABC = 90°.

By using the Pythagoras theorem,

Let h be the diagonal of the rectangle.

Base² + Height² = Diagonal²

⇒ 28² + 21² = h²

⇒ 784 + 441 = h²

⇒ 1,225 = h²

⇒ h = $\sqrt{1,225}$

⇒ h = 35 cm

Diagonal of rectangle = Diameter of circle.

Radius = $\dfrac{d}{2}$ = $\dfrac{35}{2}$ = 17.5 cm

Area of shaded portion = Area of circle - Area of rectangle

= πr² - lb cm²

= $\dfrac{22}{7}$ x 17.5² - 28 x 21 cm²

= $\dfrac{22}{7}$ x 306.25 - 28 x 21 cm²

= 22 x 43.75 - 588 cm²

= 962.5 - 588 cm²

= 374.5 cm²

Hence, area of the shaded portion = 374.5 cm².