Material by the IntegralPaso project. Conditions and limits are stated in each guide; external teaching review is pending.
On a symmetric interval an integrable odd function has integral zero; an even function lets you double the positive half. Periodicity splits intervals into full periods and remainders.
Common mistake
Oddness does not guarantee convergence with a singularity.
Step-by-step example
Check that x³ is odd.
The interval is symmetric and the function is continuous.
The contributions cancel.