A function f(t) is defined as
f(t) = p - t for 0< t< p
Write down the even extension of f(t) for -p< t< 0.
Determine the Fourier cosine series, and hence, calculate the Fourier series approximation for f(t) up to the 5th harmonics when t= 1.57. Use p = 3.142. Give your answer to 3 decimal places.