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:

Step-by-step explanation:
The equation for photon energy is given by:

Where:

This equation telling us that the higher the frequency of the photon, the greater its energy. And the longer the photon wavelength, the lower its energy.
So, replacing the data provided in the previous equation:

Brand b is 2 cents cheaper than brand a because it is 14 cents per ounce and brand a is 16 cents per ounce you do 1.68 divided by 12 and 1.28 divided by 8
Sam would have to pay $510 to buy 5 shirts and 2 suck belts.
Step-by-step explanation:
Let,
Cost of one shirt = x
Cost of one belt = y
According to given statement;
6x+4y = 660 Eqn 1
x = 3y Eqn 2
Putting value of x from Eqn 2 in Eqn 1

Dividing both sides by 22

Putting y=30 in Eqn 2

One shirt costs $90 and one belt cost $30.
Price of 5 shirts = 90*5 = $450
Price of 2 belts = 30*2 = $60
Total = 450+60 = $510
Sam would have to pay $510 to buy 5 shirts and 2 suck belts.
Keywords: linear equation, addition
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12.25x2=24.50 (width x2)
24.50-1=23.50 (length)
Area= LxW
=23.50x12.25
=287.88 feet