A circular wire of radius 15 cm is cut and bent so as to lie along the circumference of a loop of radius 120 cm.
Question:
A circular wire of radius 15 cm is cut and bent so as to lie along the circumference of a loop of radius 120 cm. Write the measure of the angle subtended by it at the centre of the loop.
Solution:
Circumference of the circle of radius 15 cm:
$2 \pi \mathrm{r}$
$=2 \times 3.14 \times 15 \mathrm{~cm}$
$=94.2 \mathrm{~cm}$
Now, 94.2 cm will be the length of arc
We know:
$l=r \theta$
Here, $\theta$ is measured in radians.
$\therefore 94.2=120 \times \theta$
$\Rightarrow \theta=0.785$ radians
$45^{\circ}=\frac{\pi}{4}=\frac{22}{7 \times 4}=0.785$ radians
Therefore, the angle subtended by it at the centre of the loop is $45^{\circ}$.