*Five Key Points*

*The Sine Function*

The first key point occurs at an average value for the sine function, we start at the left end point and proceed to the right end point moving in quarter-period increments. The second key point for the sine function is a maximum value of the function. The third key point for the sine function is an average value. The fourth key point is a minimum value. The right end point is the same value as the left end point.

*The Cosine Function*

The first key point occurs at a maximum for the cosine function, we start at the left end point and proceed to the right end point moving in quarter-period increments. The second key point for the cosine function is an average value of the function. The third key point for the cosine function is a minimum. The fourth key point is another average value. The right end point is a maximum value.