Page 75 - WCS - Electrical

WORKSHOP CALCULATION & SCIENCE - CITS

60° 22
144 = x x r² cm²
360° 7
r² = 274.91 cm²
r = 274.91 = 16.58 cm

3 Find the area of the sector whose angle is 1050, and the perimeter of sector of circle is 18.6 cm.

Given:
Perimeter of a sector of a circle = 18.6 cm
Angle of sector of circle = 105°

To find:
Area = ?
Solution:
θ
Length of Arc (l) = x 2πr unit
360°
105° 22
l = x 2 x x r
360° 7
= 1.83r

Perimeter (P) = l + 2r unit

18.6 = 1.83r + 2r

3.83r = 18.6 cm
18.6
r = = 4.86 cm
3.83
θ
Area A = x πr² unit²
360°
105° 22
= x x (4.86) cm²
360° 7
= 21.65 cm²

4 Find the area, if the radius is 12.4 cm and the perimeter of a sector of a circle is 64.8 cm.

Given:
Perimeter P = 64.8 cm
Radius r = 12.4 cm
To find:
Area A = ?

Solution:
Perimeter P = l + 2r unit
l = P - 2r unit

62

CITS : WCS - Electrical - Exercise 5