设a=1/x,则当x→∞时,a→0.
故,原式=lim(a→0)((sina+cosa)^(1/a))
=e^(lim(a→0)(ln(sina+cosa)/a))
=e^(lim(a→0)((ln(sina+cosa))'/a')
=e^(lim(a→0)((cosa-sina)/(sina+cosa))
=e^1=e
(sin(1/x)+cos(1/x))^x=(cos(1/x)*(1+tan(1/x)))^x=cos(1/x)^x *(1+tan(1/x))^x ;
cos(1/x)^x->1 (x->∞); (1+tan(1/x))^x~(1+1/x)^x ->e(x->∞),
∴所求极限=1*e=e
这,x次方.............