-f(x,y)等于f(-x,-y)吗
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例如
∫∫f(x,y)dxdy=∫∫f(x,y)dxdy=∫∫f(x,y)dxdy+∫∫f(x,y)dxdy其中∫∫f(x,y)dxdy(令x=-u,y=-v)=∫∫f(-u,-v)d(-u)d(-v)=∫∫f(-x,-y)dxdy(因为D1和D2关于原点对称)故∫∫f(x,y)dxdy=∫∫[f(x,y)+f(-x,-y)]dxdy当f(x,y)=-f(-x,-y)时,上式为0.
咨询记录 · 回答于2022-06-15
-f(x,y)等于f(-x,-y)吗
不一定
例如∫∫f(x,y)dxdy=∫∫f(x,y)dxdy=∫∫f(x,y)dxdy+∫∫f(x,y)dxdy其中∫∫f(x,y)dxdy(令x=-u,y=-v)=∫∫f(-u,-v)d(-u)d(-v)=∫∫f(-x,-y)dxdy(因为D1和D2关于原点对称)故∫∫f(x,y)dxdy=∫∫[f(x,y)+f(-x,-y)]dxdy当f(x,y)=-f(-x,-y)时,上式为0.
就不成立