lim(sin1/x∧2+cos1/x)^(x2) (x→∞) 对原式取对数,若原式极限为E1,取完之后极限为E2,则lnE1=E2,E1=e^E2
lim ln((sin1/x∧2+cos1/x)^(x2) ) (x→∞)
=lim (x2) ln(sin1/x∧2+cos1/x) (x→∞)
=lim ln(sin1/x∧2+cos1/x)/(1/x2) (x→∞)
=lim ln(sint∧2+cost)/(t2) (令1/x=t,t→0)
=lim (cost∧2·2t-sint)/(2t(sint∧2+cost)) (洛贝塔法则,t→0)
=lim(2tcost∧2-sint)/2t (t→0)
=lim(2cost∧2+2t·(-sint∧2)·2t-cost)/2 (洛贝塔法则,t→0)
=(2+0-1)/2=1/2
则原式等于√e