CPM Homework Help : INT3 Problem 10-48

Use your knowledge of the unit circle to explain why the graphs of $y = \text{sin}\left(θ\right)$ and $y = \text{cos}( \theta - \frac { \pi } { 2 } )$ are the same.

Hint:

$\frac{\pi}{2}\text{ is equivalent to } 90^\circ.$

Sketch a unit circle. Choose any angle. Find the sine and cosine of the angle. Now subtract $90^\circ$ from your angle and find the sine and cosine again. What happened? If you draw an accurate reference triangle, it will help you see what is going on here.