Find Amplitude, Period, and Phase Shift y=cos(2/3x)

$y = \cos (\frac{2}{3} x)$

Use the form $a \cos (b x - c) + d$ to find the variables used to find the amplitude, period, phase shift, and vertical shift.

$a = 1$

$b = \frac{2}{3}$

$c = 0$

$d = 0$

Find the amplitude $| a |$ .

Amplitude: $1$

Find the period of $\cos (\frac{2 x}{3})$ .

The period of the function can be calculated using $\frac{2 π}{| b |}$ .

$\frac{2 π}{| b |}$

Replace $b$ with $\frac{2}{3}$ in the formula for period.

$\frac{2 π}{| \frac{2}{3} |}$

$\frac{2}{3}$ is approximately $0.\overline{6}$ which is positive so remove the absolute value

$\frac{2 π}{\frac{2}{3}}$

Multiply the numerator by the reciprocal of the denominator.

$2 π \frac{3}{2}$

Cancel the common factor of $2$ .

Factor $2$ out of $2 π$ .

$2 (π) \frac{3}{2}$

Cancel the common factor.

$2 π \frac{3}{2}$

Rewrite the expression.

$π \cdot 3$

Move $3$ to the left of $π$ .

$3 π$

Find the phase shift using the formula $\frac{c}{b}$ .

The phase shift of the function can be calculated from $\frac{c}{b}$ .

Phase Shift: $\frac{c}{b}$

Replace the values of $c$ and $b$ in the equation for phase shift.

Phase Shift: $\frac{0}{\frac{2}{3}}$

Multiply the numerator by the reciprocal of the denominator.

Phase Shift: $0 (\frac{3}{2})$

Multiply $0$ by $\frac{3}{2}$ .

Phase Shift: $0$

List the properties of the trigonometric function.

Amplitude: $1$

Period: $3 π$

Phase Shift: None

Vertical Shift: None