Solution
= Solution
Square the Fourier <series>, integrate, and use orthogonality; cross terms vanish. This gives $\int_{-1}^1|f|^2=a_0^2/2+\sum_{n\ge1}(a_n^2+b_n^2)$.
= Solution
Square the Fourier <series>, integrate, and use orthogonality; cross terms vanish. This gives $\int_{-1}^1|f|^2=a_0^2/2+\sum_{n\ge1}(a_n^2+b_n^2)$.