# What is the period and frequency for 5cos20t?

The Period is given using $20$ in the form of: $\left(p e r i o d\right) = \frac{2 \pi}{\textcolor{red}{20}} = \frac{\pi}{10} \sec$, that represents the time taken to complete one oscillation.
The Frequency is $f = \frac{1}{p e r i o d} = \frac{10}{\pi} {s}^{-} 1 \left(H e r t z\right)$, that represents the number of oscillations in $1 \sec$.