about Inequalities

find the maximum and minimum values of thefollowing and find
the corresponding values of x，where 0°≦x≦ 360
1. 4+5Cos2x
Sol
0<=x<=360度
0<=2x<=720度
－1<=Cos2x<=1
－5<= 5C os2x<=5
－1<=4+ 5C os2x<=9
when min=－1，Cos2x=-1 =>2x=180度 or 2x=540度 =>x=90度 or x=270度
when max=9，Cos2x=1=.2x=0 or 2x=360度 or 2x=720度
=>x=0or x=180度or x=360度

find the maximum and minimum values of the following and find the corresponding values of x ,where 0°≦x≦360°
1.
-1≦cos2x≦1
-5≦5cos2x≦5
-1≦4+5cos2x≦9
When cos2x = -1,
2x = pi/2
x = pi/4
When cos2x = 1,
2x = 0 or pi
x = 0 or pi/2