Answer:
Tsin(theta) doesn't work during SHM because its direction of motion is zero.
Tsin(theta) is not considered as a restoring force because it is perpendicular to the direction of motion.
Explanation:
The component of tension T which T sin(theta) doest not work at the highest point of the swing because its direction of motion is zero.
Workdone = Force × distance
Workdone = Tsin(theta) × cos90° = Tsin(theta) × 0 = 0
A restoring force is SHM is always directed towards the equilibrium position and responsible for oscillatory motion.
Tsin(theta) changes it's direction throughout the oscillation.
Tsin(theta) is not considered as a restoring force at that because it is perpendicular to the direction of motion.
