求定积分∫(1+sinx)^2dx 从-π/2到π/2

如题所述

第1个回答  2013-02-01
∫(1+sinx)^2dx 从-π/2到π/2
= ∫(- π/2→π/2) (1 + 2sinx + sin²x) dx
= ∫(- π/2→π/2) (1 + sin²x) dx + 2∫(- π/2→π/2) sinx dx
= 2∫(0→π/2) (1 + sin²x) dx + 0
= 2∫(0→π/2) [1 + (1 - cos(2x))/2] dx
= 2∫(0→π/2) [3/2 - (1/2)cos(2x)] dx
= 2[3x/2 - (1/4)sin(2x)] |(0→π/2)
= 2[3/2 * π/2 - 0]
= 3π/2本回答被网友采纳
第2个回答  2013-02-01
∫(1+sinx)²dx
= ∫(1 + 2sinx + sin²x)dx
= x - 2cosx + ∫sin²x)dx
= x - 2cosx + (1/2)∫[1 - cos(2x)]dx
= x - 2cosx + x/2 - (1/4)∫cos(2x)d(2x)
= 3x/2 - 2cosx - [sin(2x)]/4
从-π/2到π/2:
定积分 = 3π/4 - 0 - 0 - [(-3π/4) - 0 - 0] = 3π/2
第3个回答  2013-02-01
∫(- π/2→π/2) (1 + sinx)² dx
= ∫(- π/2→π/2) (1 + 2sinx + sin²x) dx
= ∫(- π/2→π/2) (1 + sin²x) dx + 2∫(- π/2→π/2) sinx dx
= 偶函数 + 奇函数

= 2∫(0→π/2) (1 + sin²x) dx + 0
= 2∫(0→π/2) [1 + (1 - cos(2x))/2] dx
= 2∫(0→π/2) [3/2 - (1/2)cos(2x)] dx
= 2[3x/2 - (1/4)sin(2x)] |(0→π/2)
= 2[3/2 * π/2 - 0]
= 3π/2

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