设z=cos(x*2y),则全微分dz=?
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我来试试吧...z=e^xy*cos(x+y)Z'x=ye^xycos(x+y)-e^xysin(x+y)Z'y=xe^xycos(x+y)-e^xysin(x+y)故dZ=[ye^xycos(x+y
∂z/∂x=2xy∂z/∂u=x²所以dz=2xydx+x²dy
z'x=-2xyf'(x²-y²)/f^2(x²-y²)z'y=[f(x²-y²)+2y^2f'(x²-y²)]/f^2
sin(x+y)sin(x-y)=[sinxcosy+sinycosx][sinxcosy-cosxsiny]=(sinxcosy)^2-(cosxsiny)^2=(1-cos^2y)cos^2y-c
z'x=2e^(2x+y)z'y=e^(2x+y)所以dz=2e^(2x+y)dx+e^(2x+y)dy
全微分的定义:函数z=f(x,y)的两个偏导数f'x(x,y),f'y(x,y)分别与自变量的增量△x,△y乘积之和,即为f'x(x,y)△x+f'y(x,y)△y,若该表达式与函数的全增量△z之差在
D.是f(x,y)的极小值点
注意其结合性.先计算+=右面的部分.z--为先运算再自减,++x为先自增后运算.所以按照结合性,+=右面自左向右运算,z--时z=3运算后然后变成2,++x变成2,x的值自增加为2.所以整个式子为y+
对x^2+2y^2+3z^2=18两边对x求导有:2x+6zəz/əx=0,所以əz/əx=-x/3z同理,该方程两边对y求导有:4y+6zəz/
再问:非常感谢,还要问大侠一道题面目。曲线y=x³+3x的拐点坐标为???再答:y'=3x²+3y''=3x令y"=0,得x=3当x=3时,y=36所以拐点坐标(3,36)
y=cosx的递增区间是[2kπ-π,2kπ]所以2kπ-π
x^2+y^2+z^2=cos^2φcoc^2Θ+cos^2φsin^2Θ+sin^2φ=1.F=x^2+y^2+z^2Fx=2xFz=2zz对x的偏导数=一Fx/Fz=一x/z.
z=y*cos(x+y)对x求偏导得y*(-sin(x+y))=-y*sin(x+y)对y求偏导得cos(x+y)+y*(-sin(x+y))=cos(x+y)-y*sin(x+y)所以dz=-y*s
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我来试试吧...x²+2y²+3z²=18,两边微分2xdx+4ydy+6zdz=0dz=-x/(3z)dx-2y/(3z)dy
dz=Z'xdx+Z'ydy=2xcos(x^2+y^2)dx+2ycos(x^2+y^2)dy
dz=[2e^(2x+y)]dx+[e^(2x+y)]dy
再问:啊不好意思搞错了。。是z=e^(x^2+y^2),求dz,谢谢你帮我解答一下吧。。再答:
zx=2xzy=3y²dz=2xdx+3y²dy再问:谢谢!再问这位大侠一题若函数u(x,y)=y/x则du|(1,1)=?注:(1,1)在|的右下角再答:ux=-y/x²
∵正实数x,y,z满足x+2y+z=1,∴1x+y+9(x+y)y+z=x+y+y+zx+y+9(x+y)y+z=1+y+zx+y+9(x+y)y+z≥1+2y+zx+y×9(x+y)y+z=7,当且