f(sinx)^2 d(x)和cos(x)^2 d(x) 求不定积分哦

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f(sinx)^2 d(x)和cos(x)^2 d(x) 求不定积分哦

f(sinx)^2 d(x)和cos(x)^2 d(x) 求不定积分哦
f(sinx)^2 d(x)和cos(x)^2 d(x) 求不定积分哦

f(sinx)^2 d(x)和cos(x)^2 d(x) 求不定积分哦
解法一:二倍角公式作三角变形、凑微分
∫sin²xdx
=∫1/2-cos(2x)/2dx
=(∫dx)/2-[∫cos(2x)d(2x)]/4
=x/2-sin(2x)/4+C
=x/2-sinxcosx/2+C
∫cos²xdx
=∫1/2+cos(2x)/2dx
=(∫dx)/2+[∫cos(2x)d(2x)]/4
=x/2+sin(2x)/4+C
=x/2+sinxcosx/2+C
解法二:分部积分法得出循环
∫sin²xdx
=∫sinx•sinxdx
=-∫sinxdcosx
=-(sinxcosx-∫cosxdsinx)
=∫cos²xdx-sinxcosx
=∫1-sin²xdx-sinxcosx
=∫dx-∫sin²xdx-sinxcosx
=x-sinxcosx-∫sin²xdx
2∫sin²xdx=x-sinxcosx
∫sin²xdx=x/2-sinxcosx/2+C
∫cos²xdx
=∫cosx•cosxdx
=∫cosxdsinx
=sinxcosx-∫sinxdcosx
=sinxcosx+∫sin²xdx
=sinxcosx+∫1-cos²xdx
=sinxcosx+∫dx-∫cos²xdx
=x+sinxcosx-∫cos²xdx
2∫cos²xdx=x+sinxcosx
∫cos²xdx=x/2+sinxcosx/2+C