Question

sketch one cycle of the cosine function y= – cos 3θ

Answer 1

hmmm same as the other you posted... is the graph of y= cos(θ), but with a negative Amplitude of -1, and a B component of 3

let's check the period again  $\bf \cfrac{2\pi }{B}\iff \cfrac{2\pi }{3}$

so, is the same graph, with a period of  $\bf \cfrac{2\pi }{3}$ and the negative amplitude will simply, retain the same midline, but the graph will be turned upside-down

Answer 2

Answer:

 Refer the attached graph            

Step-by-step explanation:

Given : Function $y=-cos3\theta$

To Sketch the given function :

General form:   $y=\alpha cos(\beta\theta)$

where $\alpha$=amplitude and $\frac{2\pi}{\beta}$ = period

According to question,  $y=-cos3\theta$

$\alpha$=-1 and  $\frac{2\pi}{3}$ = period

From $(0,\frac{2\pi }{3} )$ cosine function sketch refer the attached graph .