Let's replace **cos( )** with **sin( ) **in the following
equation:

Then we have the following equation:

As before, when **cos( )** is replaced with **sin( )**, the graph is
rotated /2*k*
radians.

Examples

Conclusions: Replacing cosine with sine

When **cos( )** is replaced with **sin( )** in the
equation

we have

The graph is rotated /2*k*
radians.