Find the period and amplitude.
$y = \frac { 4 } { 5 } \cos \frac { 4 x } { 5 }$
A)Period: 2 $\pi$; Amplitude: 1
B)Period: $\frac { \pi } { 2 }$ ; Amplitude: $\frac { 1 } { 5 }$
C)Period: $\pi$; Amplitude: $\frac { 5 } { 4 }$
D)Period: $\pi$; Amplitude: 5
E)Period: $\frac { 5 \pi } { 2 }$ ; Amplitude: $\frac { 4 } { 5 }$

Question

Find the period and amplitude. 
 $y = \frac { 4 } { 5 } \cos \frac { 4 x } { 5 }$ 
A)Period: 2 $\pi$; Amplitude: 1
B)Period: $\frac { \pi } { 2 }$ ; Amplitude: $\frac { 1 } { 5 }$
C)Period:  $\pi$; Amplitude: $\frac { 5 } { 4 }$
D)Period:  $\pi$; Amplitude: 5
E)Period: $\frac { 5 \pi } { 2 }$ ; Amplitude: $\frac { 4 } { 5 }$

Quizplus · Accepted Answer

The period of a function $y = a \cos(bx)$ is given by $\frac{2\pi}{|b|}$, and the amplitude is $|a|$. For $y = \frac{4}{5} \cos\left(\frac{4x}{5}\right)$, $a = \frac{4}{5}$ and $b = \frac{4}{5}$, so the period is $\frac{2\pi}{\left|\frac{4}{5}\right|} = \frac{5\pi}{2}$ and the amplitude is $\left|\frac{4}{5}\right| = \frac{4}{5}$.

Find the Period and Amplitude y=45cos⁡4x5y = \frac { 4 } { 5 } \cos \frac { 4 x } { 5 }y=54​cos54x​

Find the Period and Amplitude $y = \frac { 4 } { 5 } \cos \frac { 4 x } { 5 }$