題目 Problem Part I Multiple Choice (A) ∫−ππsinmxsinnx dx=0\int_{-\pi}^{\pi}\sin mx\sin nx\,\mathrm{d}x=0∫−ππsinmxsinnxdx=0 for all m,n∈Nm,n\in\mathbb{N}m,n∈N. (B) ∫−ππsinmxcosnx dx=0\int_{-\pi}^{\pi}\sin mx\cos nx\,\mathrm{d}x=0∫−ππsinmxcosnxdx=0 for all m,n∈Nm,n\in\mathbb{N}m,n∈N. (C) ∫−ππcosmxcosnx dx=0\int_{-\pi}^{\pi}\cos mx\cos nx\,\mathrm{d}x=0∫−ππcosmxcosnxdx=0 for all m,n∈Nm,n\in\mathbb{N}m,n∈N. (D) ∫−ππsinmxcosnx dx=0\int_{-\pi}^{\pi}\sin^m x\cos^n x\,\mathrm{d}x=0∫−ππsinmxcosnxdx=0 for all m,n∈Nm,n\in\mathbb{N}m,n∈N. 解答
