Show That the Equation Is Not an Identity by Finding $y = \sin 2 \pi l t + \sin 2 \pi h t$

Multiple Choice

Show that the equation is not an identity by finding a value of x for which both sides are defined but not equal.
-The sound produced by touching each button on a touch-tone phone is described by $y = \sin 2 \pi l t + \sin 2 \pi h t$
where $l$ and h are the low and high frequencies (cycles per second) in the figure shown.



Use a calculator to find the graph of the sound emitted by touching the 3 key in a $[ 0,0.01,0.001 ]$ by $[ - 2,2$ , 1] viewing rectangle.

A)

B)

C)

D)