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: the answer is 12
Step-by-step explanation:
Answer:
y = -3x -2
Step-by-step explanation:
parallel lines have same slope
line d: slope (m) = -3
y intercept (b) = -2
equation y = mx + b y = -3x -2
Answer:
B.
Step-by-step explanation:
AC is a common side, ∠ACD = ∠ACB and CD = BC ⇒ ΔACD and ΔABC <span>are congruent (SAS definition).
</span>Congruent triangles have exactly the same three angles, so ∠D = ∠B.<span>
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