Page 14 - Grab Me SPM Add Mathematics Form 4,5

120
State the magnitude of angles (a) a, (b) b and (c) q 1.2 Arc Length of a Circle
(i) in degrees,
(ii) in radians, in terms of π, • The formula for the arc length of a circle is
(iii) in radians. Give the correct answer to four given by:
significant figures.
[Use π = 3.142] Arc length, s = rq
where q is the angle in radians.
Solution
• Note the diagram below.
(a) (i) a = 45°
(ii) a = 45° × π = π rad A
180° 4
3.142 r
(iii) a = 4 = 0.7855 rad
(b) (i) b = 90° ©PAN ASIA PUBLICATIONS C
θ
O
π π
(ii) b = 90° × 180° = 2 rad
3.142
(iii) b = = 1.571 rad
2
(c) (i) q = 135° B
π
(ii) q = 135° × 180° = 3 π rad Perimeter of the segment ACB
4
3 = Arc length ACB + Length of chord AB
(iii) q = 4 (3.142) = 2.357 rad

Ch 1_Grab Me SPM AddMaths F5.indd 120 13/05/2022 9:06 AM