计算定积分,如图

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计算定积分,如图

计算定积分,如图
计算定积分,如图

计算定积分,如图
(1)
∫[1,2]1/x(x+1)dx
=∫[1,2][1/x-1/(x+1)]dx
=∫[1,2]1/xdx-∫[1,2]1/(x+1)dx
=lnx|[1,2]-ln(x+1)|[1,2]
=ln2-0-(ln3-ln2)
=2ln2 -ln3
(2)
∫[-a,a]|x|dx
=∫[-a,0]-xdx+∫[0,a]xdx
=-1/2x^2|[-a,0]+1/2x^2|[0,a]
=-1/2a^2+1/2a^2
=0