Find the angle subtended at the centre of a circle of radius 'a' by an arc of length (a pie/4 ) cm

Answer 1

Angle α (in radians) subtended at the centre of a circle of radius R by an arc of length A is
α = A/R radians
= 180A/πR degrees

Example:
Arc = π/2 m
Radius = 3 m
Angle = (π/2)/3 radian
=π/6 radian

Answer 2

all the way around = 2 pi a

fraction of circumference = (a pi/4) /(2 pi a)

= 1/8

(1/8) 360 = 45 degrees = pi/4 radians