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.