设f(x，y)=esin(z+2y),求fx(0,π/4)；fy(0,π/4)．
【正确答案】：fx(x，y)=-e-x sin(x+2y)+e-xcos(x+2y)， fy(x，y)=2e-xcos(x+2y)， fx(0,π/4)=-sin(π/2)+cos(π/2)=-1， fy(0,π/4)=2•1•cos(π/2)=0.
设f(x，y)=esin(z+2y),求fx(0,π/4)；fy(0,π/4)．
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