Answer:
above is the answer to the question
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:
b = - 21
Step-by-step explanation:
calculate m using the gradient formula
m = ( y₂ - y₁ ) / ( x₂ - x₁ )
with (x₁, y₁ ) = (- 4, - 5) and (x₂, y₂ ) = (- 6, 3)
m =
=
= - 4
y = - 4x + b ← is the partial equation
to find b substitute either of the 2 given points into the partial equation
using (- 4, - 5 ), then
- 5 = 16 + b ⇒ b = - 5 - 16 = - 21