企源知识库

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