Answer: see proof below
<u>Step-by-step explanation:</u>
Use the Sum & Difference Identity: cos (A + B) = cos A · cos B - sin A · sin B
Recall the following from Unit Circle: cos (π/2) = 0, sin (π/2) = 1
cos (π) = -1, sin (π) = 0
Use the Quotient Identity: 
<u>Proof LHS → RHS:</u>
Quotient: tan x
LHS = RHS 
Answer: The tall cliff is 118.20 feet tall and the short cliff is 70.32 feet tall.
If you draw a picture with 2 cliffs and a river in the middle, you have find 2 right triangles. In each triangle the adjacent side to our known angle is the river of 90 feet. And the unknown side is the opposite leg.
Therefore, we can set up a tangent equation.
From the top of the short cliff to the top of the tall cliff, we can right and solve the following trig equation:
tan(28) = x /90
x = 47.88
From the top of the short cliff to the bottom, we can right and solve the following trip equation.
tan(38) = x/90
x = 70.32
The 70.32 is also the height of the short cliff. And adding the two answers together will give you the height of the tall cliff.
Answer:
n = 2b + 4
Step-by-step explanation:
4 years older = +4
2 times his brother = 2b
n= 2b+4
U call it keep change change. keep 15.7. change it to subtract and change -3.45 to just 3.45 (positive not negative)
(35 + 47 + 42 + x) / 4 = 50
(124 + x) / 4 = 50....multiply both sides by 4, cancelling the 4 on the left side.
124 + x = 50 * 4
124 + x = 200
x = 200 - 124
x = 76 <===
