Question 863378
The cos function has a maximum value of 1. 
The multiplier in front of it generates the multiplier for the displacement.
Max. displacement : {{{7}}}
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The multiplier for t is the frequency. 
{{{f=(2/3)pi}}}
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The time required to complete one cycle is the period. 
{{{P=(2pi)/f}}}
{{{P=(2pi)/((2/3)pi)}}}
{{{P=3}}}
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{{{graph(300,300,-7,7,-7,7,-7cos((2/3)pi*x)))}}}