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 
1/3 Probability both are red
red picked first:
6/10
red picked second:
5/9 (9 as first red marble not replaced so 5 red marbles remaining and 4 blue marbles still)
6/10 * 5/10 = 1/3
Hope that helps!!
Change 30 hours into minutes, then divide by 20 and 25
Answer: 3000 stamps
Step-by-step explanation:
Given
Chris and Josh have 1800 stamps
Josh and Jessica have 2200 stamps
Jessica and Chris have 2000 stamps
Suppose Chris, Josh, and Jessica have
stamps

Thus, all three have 3000 stamps