Question

How do you write a cosine equation with max= 21, min= 15 and period=15?

Answer 1

`x= B + 3 cos ( (2pi)/15 t + E)`, where B and E are arbitrary constants.

Explanation:

The general form of cosine wave with axis parallel to t-axis, axis about which it oscillates x = B, amplitude A, period P and epoch (shift) E is

`x - B + A cos (( (2pi)/P)t + E)`.

Here 2 A = maximum x - minimum x `= 21-15=6`. So, A = 3.

The period `(2pi)/P= 15`. So, `P=(2pi)/15`..

Thus, this coscine oscillation is given by

`x = B + 3 cos ((2pi)/15 t + E )`, where B and E are at your choice.