F.4 Maths (sin)

sin^2 x + sinxcosx - 2cos^2 x = 0
tan^2x + tanx - 2 = 0
(tanx -1)(tanx+2) = 0
therefore , tanx = 1 or tanx =-2
x = 45,225 or x = 117,297

2007-08-29 02:10:50 補充：
要check 番ans , 唔岩既就reject.

2007-08-29 02:16:14 補充：
sinx = 1 cosx (sinx - cosx)^2 = 1sin^2 -2cosxsinx cos^2x = 1 1 - 2cosxsinx = 1-2cosxsinx = 0-sin2x = 0sin2x = 0 2x = 180 (as 0