Question

which of the following are identities?
tan(x-pi)=tan x
cos(x+y)+cos(x-y)=2cosxcosy
cos(x+y)-cos(x-y)=2cosxcosy
sin(x+y)+sin(x-y)=2cosxsiny

check all that apply

Answer 1

wtf type math is this??? o.0

Answer 2

its pre-cal _-_ @adajiamcneal

Answer 3

oh :O well I google it and it said that a and c are the right answers

Answer 4

its a and b but thanks for the help :-) @adajiamcneal

Answer 5

I was half right :) haha pero your welcome