A..................................................................................................
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 
Answer:
8/35 is correct
Step-by-step explanation:
Just multiply the numerator by numerator and denominator by denominator, then simplify
The right answer for the question that is being asked and shown above is that: In the function f(x) = 4(x2 − 6x + ____) + 20, what number belongs in the blank to complete the square?
x2 - 6x + 9
So the answer on the blank space is 9. It should be a perfect square.
= 6/2
= 3^2
= 9