Answer: see proof below
<u>Step-by-step explanation:</u>
Given: A + B + C = π and cos A = cos B · cos C
scratchwork:
A + B + C = π
A = π - (B + C)
cos A = cos [π - (B + C)] Apply cos
= - cos (B + C) Simplify
= -(cos B · cos C - sin B · sin C) Sum Identity
= sin B · sin C - cos B · cos C Simplify
cos B · cos C = sin B · sin C - cos B · cos C Substitution
2cos B · cos C = sin B · sin C Addition
Division
2 = tan B · tan C

<u>Proof LHS → RHS</u>
Given: A + B + C = π
Subtraction: A = π - (B + C)
Apply tan: tan A = tan(π - (B + C))
Simplify: = - tan (B + C)

Substitution: = -(tan B + tan C)/(1 - 2)
Simplify: = -(tan B + tan C)/-1
= tan B + tan C
LHS = RHS: tan B + tan C = tan B + tan C 
Answer:
213$
Step-by-step explanation:
24$ on headphones
189$ left
so you add the use and what is left an u get 213$ do not forget to write $ when u are finished :)
Answer:
<u>8 and 4</u>
Step-by-step explanation:
8 + 4 = 12
8 - 4 = 4
Answer:
-12
Step-by-step explanation:
(-4) - 8
Keep Flip Change
Keep
(-4)
Flip
- to +
Change to opposite
8 to -8
Result
-4 + -8 = -12