Given the interval pi/2<alpha<pi, simplify into one trig function ​

1. TRUE
2. false - compare to 3.
3. TRUE - compare to 4.
4. TRUE - the sum of exernal angles of any convex polygon is 360°
5. false - compare to 4.
6. false - compare to 7.
7. TRUE - the angles are supplementary
8. false - compare to 4.

The true statements are 1, 3, 4, 7.