Find the area of the shaded region in the following figure, if AC = 24 cm, BC = 10 cm and O is the centre of the circle. (Use π = 3.14)
It is given a triangle ABC is cut from a circle.
$A C=24 \mathrm{~cm}$
$B C=10 \mathrm{~cm}$
Area of $\triangle A B C=\frac{1}{2} A C \times B C$
$=\frac{1}{2} \times 24 \times 10$
$=120 \mathrm{~cm}^{2}$
$\ln \triangle A B C$,
$\angle A C B=90^{\circ}$, Since any angle inscribed in semicircle is always right angle.
By applying Pythagoras theorem,
$A B^{2}=A C^{2}+B C^{2}$
$=24 \times 24+10 \times 10$
$=576+100$
$=676 \mathrm{~cm}^{2}$
$O A=\frac{A B}{2}$
$=\frac{26}{2} \mathrm{~cm}$
$=13 \mathrm{~cm}$
We know that the area A of circle of radius r is
$A=\pi r^{2}$
Substituting the value of radius r,
$A=3.14 \times 13 \times 13$
$=530.66 \mathrm{~cm}^{2}$
Area of semicircle $=\frac{1}{2} \pi r^{2}$
$=\frac{530.66}{2} \mathrm{~cm}^{2}$
$=265.33 \mathrm{~cm}^{2}$
Area of shaded region $=$ Area of circle $-$ Area of semicircle $-$ Area of triangle
$=530.66-265.33-120$
$=145.33 \mathrm{~cm}^{2}$