Using
∞ 1 π
2 (a_0 ^2) + Σ (a_n ^2 + b_n ^ 2) = ─ ∫ [f(x)]^2 dx
0 π -π
prove the series has the indicated sum.
Compute the first few partial sums to see the convergence is rapid.
証:
π 3
∫ (cos x)^4 dx = ─── π
-π 4
====
我知道f(x) = (cos x)^2
然後藉由移項來求
不過求出的b_n長的很奇怪，硬算的結果也不合
可以請板友們幫我看看嗎? m(_ _)m
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