Question

Show that sin(x+pi)=-sinx.

So far, I used the sum formula for sin which is sin(a+b)=sin a cos b+cos a sin b.
sin(x+pi)=sin x cos pi+cos x sin pi
I think I am supposed to do this next, but I am not sure.
sin(x+pi)=sin x cos x+sin pi cos pi
If that is right then I am not sure what to do from there. Can someone please help?

Answer 1

in(x+pi)=sin x cos pi+cos x sin pi but cosPI=-1, sin PI=0
sin(x+PI)= -sinx

Answer 2

Thanks bobpursley!!!

Answer 3

Can you please help me with one more?

Which are simplified forms of the expression tan^2T cos2T? Select all that apply. (2 answers)
a. 2sin^2T-tan^2T
b. tan^2T-2cos^2T
c. 2sin^3T/cosT
d. cos2T/cot^2T
e. 2cos^2T-tan^2T

Answer 4

(sin^2T/cos^2T)(2 cos^2 T - 1)
= 2 sin^2 T - tan^2 T