Question:
Find the lengths of the arcs cut off from a circle of radius 12 cm by a chord 12 cm long. Also, find the area of the minor segment.
Solution:
Let AB be the chord. Joining A and B to O, we get an equilateral triangle OAB.
Thus, we have:
$\angle O=\angle A=\angle B=60^{\circ}$
Length of the arc ACB:
$2 \pi \times 12 \times \frac{60}{360}$
$=4 \pi$
$=12.56 \mathrm{~cm}$
Length of the arc ADB:
Circumference of the circle - Length of the arc ACB
$=2 \pi \times 12-4 \pi$
$=20 \pi \mathrm{cm}$
$=62.80 \mathrm{~cm}$
Now,
Area of the minor segment:
Area of the sector - Area of the triangle
$=\left[\pi \times(12)^{2} \times \frac{60}{360}-\frac{\sqrt{3}}{4} \times(12)^{2}\right]$
$=13.08 \mathrm{~cm}^{2}$