Question

Find the period of the function.

y = -3 cos1/4x

Things I know:
f(x)=a cosbx
then period=2pi/b
So: -3cos1/4x
period=2pi/(1/4x)
I got that but it's not matching my choices?:

-3
3pi/4
8π
pi/4

Answer 1

Memorize this: the coefficient of x = 2pi divided by the period or:

Answer 2

\[c=\frac{2\pi}{period} \]
\[period = \frac{2\pi}{c}=\frac{2\pi}{\frac{1}{4}}=2\pi \times \times 4=8\pi \]

Answer 3

Oh I see. Thanks!

Answer 4

yw