Step 1 :

(a)

The function is $\"\"$ .

Product-to-sum formulas : $\"\"$ .

$\"\"$

The product $\"\"$ can be written as a sum of $\"\"$

Step 2 :

(b)

The method of adding y - coordinates to the graph.

The function is $\"\"$ and the interval is $\"\"$ .

Consider the composite functions as $\"\"$ and $\"\"$ .

Make a table of values in the interval $\"\"$ :

\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \

Graph the functions $\"\"$ and $\"\"$ on the same coordinate system.

(1) Draw the coordinate plane.

(2) plot the points.

(3) connect the points with a smooth curve.

The graph is :

$\"\"$