__ _cos b =1/2[sin(a+b)+sin(a-b)] a) cos b b) sin b c) sin a d) cos a

sin a

Step-by-step explanation:

let the unknown term be x.

you have to remember that:

2sinAcosB=sin(A+B)+sin(A-B)

question 1 is 8, question 2 is 9, question 3 is 24

step-by-step explanation:

now, the numbers they give you at the top are the key. from there, you just have to plug and chug! let's try 1, 2, and 3!

key: a=3, b=5, c=6

1. a+5

remember, a=3, so we plug that in to get 3+5=8

2. 15-c

c=6, so we plug that in to get 15-6=9

3. 4b

b=6, so we plug it in to get 4*6=24

time to try the rest on your own! if you put the answers below in a comment, i'll check them for you!