題組內容

4. Given a function \( f(x) = x + \pi, -\pi < x < \pi \) and evaluate the following:

(b) Use the result to show the sum of the series \[ \frac{\pi}{4} = 1 - \frac{1}{3} + \frac{1}{5} - \frac{1}{7} + \dots \] (10%)