上限和下限分别代入,然后做减法.
∫ [a→b] f(x)dx=F(b)-F(a),其中F(x)是f(x)的原函数.
本题最后两步:
1/8*x^4-x+arctanx [1→2]
=(1/8*2^4-2+arctan2)-(1/8*1^4-1+arctan1)
=(2-2+arctan2)-(1/8-1+π/4)
=7/8-π/4+arctan2
∫∫D(x^2 /y^2)dxdy,其中D是由xy=2,y=1+x^2,x=2围成的区域
∫∫D(x^2 /y^2)dxdy,其中D是由xy=2,y=1+x^2,x=2围成的区域
∫∫D(x^2 /y^2)dxdy
=∫[1,2]x^2dx ∫[2/x,1+x^2]1/y^2 dy
=∫[1,2]x^2dx (-1/y) [2/x,1+x^2]
=∫[1,2]{x^3/2-x^2/(1+x^2)}dx
=∫[1,2]{x^3/2-1+1/(1+x^2)}dx
=1/8*x^4-x+arctanx [1,2]
=7/8-π/4+arctan2
arctan1=π/4,为什么有负号?倒数第二步到最后一步不懂
∫∫D(x^2 /y^2)dxdy
=∫[1,2]x^2dx ∫[2/x,1+x^2]1/y^2 dy
=∫[1,2]x^2dx (-1/y) [2/x,1+x^2]
=∫[1,2]{x^3/2-x^2/(1+x^2)}dx
=∫[1,2]{x^3/2-1+1/(1+x^2)}dx
=1/8*x^4-x+arctanx [1,2]
=7/8-π/4+arctan2
arctan1=π/4,为什么有负号?倒数第二步到最后一步不懂
数学人气:599 ℃时间:2019-08-21 21:38:36
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