3cos–1 x = cos–1 (4x3 – 3x), 
21 , 1
x


∈



Write the following functions in the simplest form:
3 2
1
1
1
tan
x
x
−
+
− , x ≠ 0
4 1
1
cos
tan
1
cos
x
x
− 

−




+


, 0 < x < π
5 1 cos
sin
tan
cos
sin
x
x
x
x
− 

−


+


, 4
−π  < x < 3
4
π
6