已知f(x,y)=
{xy/(x2+y2),(x2+y2≠0)
0,(x2+y2≠0)
求fx(0,0),fy(0,0).
f0(0,0)=lim△x→0[f(0+△x,0)-f(0,0)]/△x =lim△x→0{[0•△x/(△x2+02)]-0}/△x=lim△x→00/△x=0 fy(0,0)= lim△y→0[f(0,0+△y)-f(0,0)]/△y =lim△y→0{[0•△y/(02+△y2)]-0}/△y=lim△y→00/△x=0
已知f(x,y)=
{xy/(x2+y2),(x2+y2≠0)
0,(x2+y2≠0)
求fx(0,0),fy(0,0).
f0(0,0)=lim△x→0[f(0+△x,0)-f(0,0)]/△x =lim△x→0{[0•△x/(△x2+02)]-0}/△x=lim△x→00/△x=0 fy(0,0)= lim△y→0[f(0,0+△y)-f(0,0)]/△y =lim△y→0{[0•△y/(02+△y2)]-0}/△y=lim△y→00/△x=0