lim(x→0)[(secx)^2-1] /(1-cosx)

lim(x→0)[(secx)^2-1] /(1-cosx)

lim(x→0)[(secx)^2-1] /(1-cosx)
=lim tan²;x/[(1/2)x²;]
=lim x²;/[(1/2)x²;]
=1/2