Frequency is defined as number of oscillation completed by an oscillating body in unit time i.e. in one second during oscillatory motion.
Equation of simple harmonic motion is given by
Where x(t) is the displacement of body at any instant of time
A is the amplitude of the body
is the phase angle at the instant of time.
Simple harmonic motion is the projection of uniform circular motion.In the above diagram P is the position of particle at at any instant of time.This motion follows the condition of SHM.simple harmonic motion is a type of periodic motion or oscillation motion where the restoring force is directly proportional to the displacement and acts in the direction opposite to that of displacement