Abbreviations:
T = True,  F = False,  NG = Neutral Geometry

9-2:

1. T. Theorem in NG.
2. T. Theorem in NG.

9-3:

1. F.
2. T. Theorem in NG.
3. F. Either all three altitudes meet at one point, or none of them meet at all.
4. T. Theorem in NG.
5. T. Theorem in NG.
6. F

9-4:

1. T. Theorem in NG.
2. T. Theorem in NG.

9-5:

1. T. Same construction as in NG (Sec 1.8).
2. T. Theorem in NG.
3. F. By Theorem 8.2.6.

9-6:

1. T. Same construction as in NG (Sec 1.8).
2. F.

9-7:

1.  
2. Yes (Chapter 1).
3. ASS: No.
   AAA: Yes, by Theorem 8.3.3.

9-8:

1. T.
2. F.
3. F.
4. T (in NG).
5. T (in NG).

9-9:

1. T.
2. F.
3. F.
4. F.

9-10:

    1-5: All are T.

9-11:

1.  
2. No.
3. Yes.
4. Yes.

9-12:

1.  
2. No.
3. No.

Additional Activities for HW 25:

1. Incenter: Yes (T in NG).
   Circumcenter: No.
   Orthocenter: No.
   Centroid: Yes.

2. No. Can construct counterexamples.

3. No, by Theorem 8.3.3.