Jawabanmu

2014-04-09T15:25:39+07:00
1. Sin^2 (a) / (-2a).(Tan a)
=1.1 / (-2).1
= -1/2

2. (cos 2x-1) / (cos 4x-1) =
(cos 2x-1) / (cos^2 2x - sin^2 2x - 1) =
(cos 2x-1) / (cos^2 2x - 1 + cos^2 2x - 1) =
(cos 2x-1) / 2(cos 2x - 1)(cos 2x + 1) = 1 / 2(cos 2x + 1) =
1 / 2(cos 2.(phi/4) + 1) = 1 / 2 (0+1) = 1 / 2