### Postulate 2.8 "Ruler Postulate" (HW Postulate 1)

The points on any line or line segment can be paired with real numbers so that given any 2 points, A and B on a line, A corresponds to 0 and B corresponds to a positive real number.

### Postulate 2.9 "Segment Addition Postulate" (HW Postulate 2)

If A, B, and C are collinear, and B is between A and C, then AB+BC=AC. or If AB+BC=AC, then B is between A and C.

### Postulate 2.10 "Protractor Postulate" (HW Postulate 3)

Given line AB and a number r between 0 and 180, there is exactly one ray with endpoint A, extending on either side of line AB, such that the measure of the angle formed is r.

### Postulate 2.11 "Angle Addition Postulate"

If B lies in the interior of <AOC, then m<AOB + m<BOC = m<AOC. If <AOC is a straight angle, and B is any point not on ray AC, then m<AOC + m<BOC = 180.

### HW Postulate 5

A line contains at least 2 points; a plane contains at least 3 points not all in one line; space contains at least 4 points not all in one plane.

### HW Postulate 7

Through any 3 points, there is at least one plane, and though any 3 noncollinear points there is exactly one plane.

### HW Theorem 2-1 "Midpoint Theorem"

If M is the midpoint of segment AB, then AM=1/2AB and MB=1/2AB.

### HW Theorem 2-2 "Angle Bisector Theorem"

If ray BX is the bisector of <ABC, then m<ABX=1/2M<ABC and m<XBC=1/2m<ABC.

### HW Theorem 2-6

If the exterior sides of 2 adjacent acute angles are perpendicular, then the angles are complementary.

### Theorem 2.6 (HW Theorem 2-7)

Angles supplementary to the same angle or to congruent angles are congruent.

Abbr. <'s suppl. to same < or congruent <'s are congruent