Use a graphing utility to graph the sound emitted by the * key on a Touch-Tone phone. See Problem 57.

Data from problem 57

On a Touch-Tone phone, each button produces a unique sound. The sound produced is the sum of two tones, given by

where l and h are the low and high frequencies (cycles per second) shown in the illustration. For example, if you touch 7, the low frequency is l = 852 cycles per second and the high frequency is h = 1209 cycles per second. The sound emitted by touching 7 is

Use a graphing utility to graph the sound emitted by touching 7.

y = sin(27lt) and y = sin(27ht)| y = sin[27 (852)t] + sin[2#(1209)t] %3D