Answer:
Identity (a) can be re-written as
which we already proven in another question, while for idenity (b)
step A is simply expressing each function in terms of sine and cosine.
step B is adding the terms on the LHS while multiplying the one on RHS.
step C is replacing the term on the numerator with the equivalent from the pithagorean identity 
First expand the brackets which will give you
then factor them
First lets start by making the denominators the same. I multiplied the 4 by 5 and 10 by 2.
-25/20 = x -14/20
Add 14/20 on both sides (do the opposite to cancel out and whatever you do to one side you need to do to the other.
You should get -11/20 = x
Answer:
x = 5.2
Step-by-step explanation:
x/(13-x) = 2/3
3x = 2(13 - x)
3x = 26 - 2x
3x + 2x = 26
5x = 26
x = 26/5
x = 5.2
