It can be represented by this expression: -20+20
We have to find the period of the parent cosine function and the period of the function showed on the graph.
Period = 2π / B, where B is the coefficient of x - term.
1. For the function: y = cos x, B = 1
Period = 2 π / 1 = 2 π = 360°.
2. For the graphed function ( from the picture ):
Period = 6 π = 1,080°