use the unit circle to investigate equivalent expressions involving the six trig functions of (x + pi) where x lies in the first quadrant. add these to your trigonometric identities table

Answer 1

adding π is equivalent to rotating halfway around the origin.
That changes the sign of x and y.
Now, you know that
sinθ = y/r
cosθ = x/r
tanθ = y/x
since both x and y have changed sign, and r is positive, what does that tell you about the trig functions?

Answer 2

that i have to use sin(pi+x)?