Fourier series and parseval's theorem

[marshmallow]

A square wave has amplitude 3 and period 5. calculate its power?

Using Fourier series for this square wave and Parseval’s
theorem, calculate the power in a signal obtained by cutting out frequencies
above 1 Hz in the square wave?

i am able to obtain the Fourier series for the square wave but i am unsure about the power and the power by cutting out frequencies above 1Hz?

Help would be much appreciated.

 

[marcusl]

Write down Parseval's theorem. What does it mean? How might it apply to your problem?