Cos x cos(-x)-sin x sin(-x)=1 certify the identity with !

Step-by-step explanation:

To answer this problem we must know the following properties.

even function

odd function

  Because..........

 Because..........

By definition

Then, the property is demonstrated:

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!