Chapter 1 - Functions and Limits - 1.3 New Functions from Old Functions - 1.3 Exercises - Page 43: 13

See the image below

To graph this function ($y=2cos3x$) by transformations, we first graph $y=cosx$ (Graph (1)). After that, we have to either: - stretch the graph vertically by a factor of $2$ (that is, $y=2cosx$) and then shrink it horizontally by a factor of $3$ (that is, $y=2cos3x$, (Graph(3)) or - shrink it horizontally by a factor of $3$ (which is $y=cos3x$, Graph(2)) and then stretch the graph vertically by a factor of $2$ (which is, $y=2cos3x$, Graph (3))