Find the angle in radian through which a pendulum swings if its length is 75cm and the tip described an arcs of length
(i) 10cm
(ii) 15cm
(iii) 21cm

(i) Length of the pendulum (r) = 75cm
Length of an arc (l) = 10cm
θ = l/r = 10/75radians = 2/15radians

(ii) Length of the pendulum (r) = 75cm
Length of an arc (l) = 15cm
θ = l/r = 15/75 radians = 1/5radians

(iii) Length of the pendulum (r) = 75cm
Length of an arc (l) = 21cm
θ = l/r = 21/75 radians = 7/25radians