Circular functions representing periodic motion that satisfy the equations

where *d* is an amount of displacement, *A* and *B* are constants determined by the specific motion, and *t* is a measurement of time are referred to as **simple harmonic motion**.

**Example 1:** If the instantaneous voltage in a current is given by the equation *E* = 204 sin 3680 *t*, where *E* is expressed in volts and *t* is expressed in seconds, find *E* if *t* = 0.27 seconds. Use 3.1416 for π.

Since sin *x* = sin ( *x* − *2k*π *)* and (993.6 *+* 2I÷2π) = 158 with a remainder of .8544,

**Example 2**: The horizontal displacement *(d)* of the end of a pendulum is *d* = *K*sin *2*π *t*. Find *K* if *d* = 12 centimeters and *t* = 3.25 seconds.