Question

Find the area of the sector of a circle of radius 5 cm, if the corresponding arc length is 3.5 cm.

Answer 1

Let the central angle of the sector be θ.

Given that, radius of the sector of a circle (r) = 5 cm

And arc length `(l)` = 3.5 cm

∴ Central angle of the sector,

θ = `("arc length"  (l))/"radius"`

⇒ θ = `3.5/5` = 0.7R   ...`[∵ θ = l/"r"]`

⇒ θ = `(0.7 xx 180/pi)^circ`  ...`[∵ 1"R" = 180^circ/pi "D"^circ]`

Now, area of sector with angle θ = 0.7

= `(pi"r"^2)/360^circ xx (0.7) xx 180^circ/pi`

= `(5)^2/2 xx 0.7`

= `(25 xx 7)/(2 xx 10)`

= `175/20`

= 8.75 cm²

Hence, the required area of the sector of a circle is 8.75 cm².