Question

sin(x−π)=−sin(x)

Answer 1

yep, thats true, do you need to prove it?

Answer 2

if so, use
\(\Large \sin (a-b) = \sin a \cos b - \cos a \sin b\)

and plug in, a =x
and b = \(\bbox[yellow]\pi\)

Answer 3

What are you allowed to use?

Answer 4

As I am sure the one you posted is used to prove the one that was given...