If the instructions for a problem ask you to use the smallest possible domain to completely graph two periods of y = 5 + 3 cos 2(x -pi/3), what should be used for Xmin and Xmax? Explain your answer.

Verified Answer :

The period of a sinusoid \(\cos 2(x-c)\) is \(\dfrac{2\pi}2=\pi\), so any range such that \(\mathrm{Xmax}-\mathrm{Xmin}=2\pi\) will give two complete periods.

Answer:

The smallest possible domain to completely graph two periods is either [0, 2π] or [-π, π].

Step-by-step explanation:

The period of cosine function [0, 2π].

The given function is

\(y=5+3\cos 2(x-\frac{\pi}{3})\)

This function can be written as

\(y=5+3\cos (2x-\frac{2\pi}{3})\)          .... (1)

The general form of cosine function is

\(y=A\cos (Bx+C)+D\)              .... (2)

where, A is amplitude, \(\frac{2\pi}{B}\), C is phase and D is midline.

From (1) and (2), we get

\(A=3,B=2C=\frac{2\pi}{3},D=5\)

\(Period=\frac{2\pi}{2}=\pi\)

The period of given function is [0,π]. So, the smallest possible domain to completely graph two periods is either [0, 2π] or [-π, π].