Question

Having a brain freeze. I am solving my problem and I have to put my reasoning but just cannot, for the life of me, remember the word that explains this step. I know its really simple and I'll feel like a noob when this gets answered lol. Help me out D:

2+cos(x+y)+cos(x+y)= 2+2cos(x+y)

Answer 1

what are you solving for x and y?

Answer 2

2+cos(x+y)+cos(x+y)= 2+2cos(x+y)
cos(x+y)+cos(x+y)= 2+2cos(x+y) - 2
2cos(x+y) = 2 - 2 + 2cos(x+y)
2cos(x+y) = 2cos(x+y)

Answer 3

a + a = 2a
let a = cos (x + y)
then
cos (x + y) + cos (x + y) = 2cos (x + y)

Answer 4

@bluepig148 , at least your solution is simpler