tentukan lim x mendekati 0 xtan 2x/cos^2 x-1

lim (x tan 2x ) / (cos^2 x - 1)
lim (x tan 2x ) / sin^2 x
lim (x/sin x). (tan 2x / sin x)
= 1. lim (tan 2x / 2x) / (sin x /x) .2
= 1.2
= 2