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:
x = -2 and y = 2
Step-by-step explanation:
The given equations are :
-5x-2y=6 ...(1)
3x+6y=6 ...(2)
Multiply equation (1) by 3. SO,
-15x-6y=18 ...(3)
Adding equation (2) and (3).
3x+6y-15x-6y = 6+18
-12x = 24
x = -2
Put the value of x in equation (1).
-5(-2)-2y=6
10-2y=6
4=2y
y = 2
So, the value of x is -2 and y is 2.
Answer:
the answer is -3/2
Step-by-step explanation:
Trust me its correct
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