求(1+xy)^[1/(x+y)] 极限

求极限lim(x,y)→(0,0) [1-cos(xy)]/xy^2. 求下列各极限 lim(x,y)→(0,1) (2-xy)/(x^2+2y) 求极限lim(x→1 y→2) (x²+y²)/xy 求二元函数极限：（x,y)趋近于(2,-1/2)时lim(2+xy)^(1/(y+xy^2)) 跪求极限Y=lim (xy+1)/x^4+y^4,当（x,y）→（0,0）, 求极限((1-根号下x^2+1)/x^3y^2)sin(xy),当x,y趋于0时 求二重极限lim[xy/(1+x^2+y^2)],x→0,y→0.求详细步骤 求极限lim(1-cosxy)/x²y²,xy都趋于0 求极限lim x→0 y→0 2xy/根号下1+xy 然后-1 {不在根号里｝ 求极限:lim xy分之{[(1+xy)开3次根号]-1},(x,y)→(0,0) 1-cos(xy)/(x^2+y^2)的极限, 求极限：1)x趋于0,y趋于1时,lim(1-xy)/(x^2+y^2)