Low pass filter output

What will be the output when a square wave of time period 1sec is applied to the input of LPF of cutoff frequency 1Hz. Please help me, I am not getting the exact expression. What if cutoff of LPF is increased to 4Hz.

• This looks like homework. Go ahead and edit your question to both share the problem as given to you, and to show us the work you've done. – TimWescott Aug 25 '20 at 17:31
• @TimWescott , Sir I found the Fourier series representation of square wave and found only the first harmonic will get pass through the LPF. So the o/p has to be a sine wave but I am not confident. – user32834 Aug 25 '20 at 17:43
• So the filter is specifically defined as having $H(f) = 1\ \forall\ |f| \le 1$ and $H(f) = 0\ \forall\ |f| > 1$? – TimWescott Aug 25 '20 at 18:27
• @TimWescott Yes Sir – user32834 Aug 26 '20 at 1:14