Dewight is proving the sum formula for the sine function. he has started his proof, what property should he use to complete the next line?

C) the difference identity for the cosine function

Step-by-step explanation:

The last line showing shows the cosine of the difference of two angles. The difference identity for the cosine function would seem to be indicated.

answer: slight chance that it will happen

step-by-step explanation:

c.

step-by-step explanation:

because first you have to add the 4x, 9x, and the 7x together and you get 20x and then you add the last numbers up and you get 5and then you put the subtraction sign in there and that's how you get the answer.