lim(x→0) (e^-x+e^x -2)/(1-cosx)
(x→0) e^-x+e^x-2 →0 1-cosx →0
lim(x→0)(e^-x+e^x-2)/(1-cosx)=lim(x→0) (e^x-e^-x)/sinx
x→0 e^x-e^-x →0 sinx→0
lim(x→0)(e^x-e^-x)/sinx=lim(x→0) (e^x+e^-x)/cosx=2
lim(x→0)(e^-x+e^x-2)/(1-cosx)=2