1. cos x -cos 3x
----------------- = tan 2x
sin 3x - sin x
2. sin x + sin 2x
-------------------- = tan x
1+cos x + cos 2x
-----------------------------------------------------
3. If tan x = 1/4 , find the values of tan 3x and tan 6x.
4. If sin A = 1/3 and A is acute, find the value of cos A+cos 2A
-----------------
1+sin A+sin 2A
5.If 36cos^2 x -3sin x=31and90。< X <180。,find the value of sin 2x
Show your steps clearly Thx !!!
更新1:
Q.4 If sin A = 1/3 and A is acute, find the value of: cos A+cos 2A ----------------- 1+sin A+sin 2A
