Trigonometric Functions

Prove that:
7. sin 3x + sin 2x – sin x = 4sin x cos
x
2
cos
3
2
x
Find sin
x
2
, cos
x
2
and tan
x
2
in each of the following :
8. tan x = −
4
3
, x in quadrant II 9. cos x = −
1
3
, x in quadrant III
10. sin x = 4
1
, x in quadrant II