Question

Which equation represents the graph shown below?y= 200cos(pi/80x)+300y= 300cos(pi/40x)+200y= 200cos(pi/40x)+300y=300cos(pi/80x)+200

Answer 1

Use one of the points in the graph. With the value of x, evaluate each function. If the result of evaluating that function is the same as the value of y, that is the equation that represents the graph.

For example, use the point (40,300)

Evaluate each function on x=40

`\begin{gathered} y=200\cos ((\pi x)/(80))+300 \\ y=200\cos ((\pi40)/(80))+300 \\ y=200\cos ((1)/(2)\pi)+300 \\ y=200\cdot0+300=300 \end{gathered}`

y=300, this result show that the output of 40 is 300, this is correct according to the graph. It means the equation that represents the graph shown is the first one.

`y=200\cos ((\pi x)/(80))+300`