求∫-π/2π/2[ln(x+)+sin2x]cos2xdx.

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问题 求∫-π/2π/2[ln(x+)+sin2x]cos2xdx.

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答案因为ln(x+[*])为奇函数, 所以∫-π/2π/2ln(x+[*])+sin2x]cos2xdx=∫-π/2π/2sin2x cos2xdx =2∫0π/2sin2x(1-sin2x)dx=2(I2-I4) =2(1/2×π/2-3/4×1/2×π/2)=π/8.

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