Question

The periodic function f(t)=2cos(4*pi*t)

Answer 1

Answer:

According to Oppenheim's signal and systems solution book and other solutions like this

Ev(cos(4πt)u(t))=1/2×(cos(4πt)u(t)+cos(4πt)u(−t))=1/2(cos(4πt))

for −∞<t<∞

is periodic and its period 1/2.

But I think it is not equal 1/2(cos4πt) at t=0 so it is not periodic because at t=0 it is equal to 1 different from other multiples of period.

I have also curious about the value of u(t)+u(−t). Is it 0, 1, or 2 ?