Answer: see proof below
<u>Step-by-step explanation:</u>
Given: cos 330 = 
Use the Double-Angle Identity: cos 2A = 2 cos² A - 1

Proof LHS → RHS:
LHS cos 165
Double-Angle: cos (2 · 165) = 2 cos² 165 - 1
⇒ cos 330 = 2 cos² 165 - 1
⇒ 2 cos² 165 = cos 330 + 1
Given: 

Divide by 2: 

Square root: 
Scratchwork: 

Since cos 165 is in the 2nd Quadrant, the sign is NEGATIVE

LHS = RHS 
Answer:
f(f(x)) = x⁴ + 2x² + 2
Step-by-step explanation:
if f(x) = x² + 1, then f(f(x)) is equal to:
f(x)² + 1
= (x² + 1)² + 1
= x⁴ + 2x² + 1 + 1
= x⁴ + 2x² + 2
Answer:
71 degrees
Step-by-step explanation:
A right angle is 90 degrees, so the answer is 90-19=71 degrees.
It would be 66 degrees because
this would equal 180 degrees
add the angles together:30+57+27=114
now subtract 180-114=66degrees
FINAL ANSWER:66degrees
6.50 * 22.5 = 146.25 dollars