# How to calculate the frequency of an AC voltage given by $e = 100\cos(\omega t)$

The standard equation of instantaneous voltage is :- $$e = e_m \sin(\omega t)$$

In this case :- $$e = 100 \cos(\omega t) \\ \implies e = 100 \sin(\omega t + \frac{\pi}{2})$$

Now, $$\omega = 2 \pi f \\ \implies f = \frac{\omega}{2 \pi}$$

If the $$\frac{\pi}{2}$$ were not present, I would have easily calculated the frequency, but how can I calculate frequency in this case?

• After ignoring the phase shift, is there a way to calculate the frequency since the value of $\omega$ is not given in the question ? – arandomguy Jun 9 '19 at 12:42