Question

If angle of arc is 60° and the length of arc is 20 cm. Find the radius of the circle from which arc is intercepted.

(a) 18.08 cm

(b) 17.07 cm

(c) 19.09 cm

(d) 18 cm

This question was addressed to me by my college director while I was bunking the class.

This interesting question is from Trigonometric Functions in section Trigonometric Functions of Mathematics – Class 11

Answer 1

Correct option is (c) 19.09 cm

To elaborate: 180 degree = π radian

1 degree = π/180 radians

60 degrees = 60* π/180 radians = π/3 radians

Angle=Arc length/Radius

π/3 = 20/Radius => Radius = 60/π = 19.09 cm.