C = 2 x π x 30 cm
C = 60 π
Arc Length (cm)_______Angle at centre ( radians )
60π____________________2π
12___________________12 / (60π) x 2π = 2/5
Pendulum swings thro` an angle of 2/5 radians = 0.4 radians
2π radians <---------->360°
0.4 radians <-------->0.4 / ( 2π ) x 360 ° = 22.9 °
Swings thro ` an angle of 22.9 °