Answer with Explanation:
Keep in mind these trigonometric Identity:
1. Cos²x - Sin² x= Cos 2 x
2. Cos 2 x = 2 Cos²x-1
3. Cos 2 x = 1 - 2 Sin²x
Now, Coming to the Problem
1 + Cos (18 x)
= 1 + Cos (2 × 9 x)
= 2 Cos ² (9 x)→→→ Cos (2 × 9 x)= 2 Cos² (9 x) - 1
66!
Surprised I got that.
360 - 42 - 42 - 72 - 72 = 132
132 / 2 = 66
If you look opposite from where the angles are given they are the same angles.
First of all, division is the opposite of multiplication. So if I
divide 72 by 3 I should get 24, since 3*24 = 72.