方法如下图所示,
请认真查看,
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建议先学习导数求导公式!!
19.y=ln[x+√(x²+a²)]
y'=[x+√(x²+a²)]'/[x+√(x²+a²)]=1/√(x²+a²)
20.y=[sinx/(x²+1)]½
y'=1/2 [sinx/(x²+1)]^(-1/2) [sinx/(x²+1)]'
=[(x²+1)cosx-2xsinx]/{2(x²+1)²√[sinx/(x²+1)]}
=[(x²+1)cosx-2xsinx]/√[4(x²+1)³sinx]
dy=[(x²+1)cosx-2xsinx]/√[4(x²+1)³sinx] dx
21.y=u^v u=sinx,v=cosx
y'=vu^(v-1) u'+u^v lnu v'
=cos²x (sinx)^(cosx-1) -sinx (sinx)^cosx lnsinx
dy=[cos²x (sinx)^(cosx-1) -sinx (sinx)^cosx lnsinx] dx