Answer:
yay u got your answer:))
but seriously what is your question?:))
I hope this helps you
(1-cosx)(1+cosx)=1+cosx-cosx-cos²x=1-cos²x=sin²x
sin²x
____
cos²x
tg²x
Answer: 
<u>Step-by-step explanation:</u>

NOTE: The sign between 4x and 7 is missing in the question you posted. I assumed it was 4x + 7 in order to solve the equation.
Answer:
regular price = $15
Step-by-step explanation:
Represent the regular price by d. Then the discount was 0.20d, and the sale price was (1 - 0.20)d, or 0.80d, which is $12.
Solving for d, we divide both sides by 0.80:
d = regular price = $15