如何求Lim[2-(xy+4)^1/2]/xy x→0 ,y→0 和Lim sin(xy)/x x→0,y→0 这两道的极限值,求解题过程!谢谢

如何求Lim[2-(xy+4)^1/2]/xy x→0 ,y→0 和Lim sin(xy)/x x→0,y→0 这两道的极限值,求解题过程!谢谢 求极限lim(x,y)→(0,0) 3xy/(xy+4)^1/2-2 求极限. lim (x→0) [√ (xy+4) -2 ]/xy (y→0)lim (x→0)(y→0)[√ (xy+4) -2 ]/xy 求极限lim(x,y)→(0,0) [1-cos(xy)]/xy^2求极限lim(x,y)→(0,0) [1-cos(xy)]/xy^2,麻烦写下过程 求极限lim(x,y)→(+∞,+∞) [(xy)/(x^2+y^2)]^xy.求极限lim(x,y)→(+∞,+∞) [(xy)/(x^2+y^2)]^xy, 求极限lim(x,y)→(0,0) [1-cos(xy)]/xy^2.求极限lim(x,y)→(0,0) [1-cos(xy)]/xy^2,麻烦写下过程 求二元函数极限：（x,y)趋近于(2,-1/2)时lim(2+xy)^(1/(y+xy^2)) 求极限lim x→0 y→0 2xy/根号下1+xy 然后-1 {不在根号里｝ 求下列各极限 lim(x,y)→(0,1) (2-xy)/(x^2+2y) 求lim(x,y)~(0,1)1-xy/x^2+y^2的极限,要详解 求极限lim(x→1 y→2) (x²+y²)/xy 求下列极限 1.lim x→0y→2 sin(xy)/x 2.lim x→0y→0 (2-√（xy+4）)/xy3.lim x→0y→0(x^2y)/(x^3-y^3) 4.limx→0y→1 xy*sin(1/(x^2+y^2)) lim[sin(xy)/xy],x趋向2,y趋向0,求极限 求lim sin(xy)/xy,x趋近于2,y趋近于0 Lim [2-根号下(xy+4)]/xy,能不能令t=xy后带入求极限?(x,y)→(0,0) lim(x,y)->(0,2)(1-3xy)^2/x lim(2-√￣（xy+4）)/xy x→0 y→0答案是-1/4 求二重极限lim[xy/(1+x^2+y^2)],x→0,y→0.求详细步骤