Answer
See the image below.
Work Step by Step
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))
