Application to solve for Fourier series coefficients?
A Fourier series has the form

$$x(t)=a_0 + \sum_{n=1}^\infty\left( a_n\cos(\frac{2\pi{}nx}{P}) + b_n\sin(\frac{2\pi{}nx}{P}) \right)$$

Can you find some choices of \$a_n\$, \$b_n\$, and \$P\$  that makes this sum turn into the function you're trying to create without doing any calculation at all?