Chapter 7.10, Problem 5P

In Problems 4 to 10, the sketches show several practical examples of electrical signals (voltages or currents). In each case we want to know the harmonic content of the signal, that is, what frequencies it contains and in what proportions. To find this, expand each function in an appropriate Fourier series. Assume in each case that the part of the graph shown is repeated sixty times per second.

Rectified half-wave; the curve is a sine function for half the cycle and zero for the other half. Let the maximum current be 5 amp. Hint: Be careful! The value of $l$ here is $1/60$, but $I(t)=$ sin t only from $t=0$ to $t=1/120.$