Remember:

Reason: An exterior angle of a triangle is greater than either of its nonadjacent interior angles.

3

213 mmm

1

2

13 mm and 23 mm

Exterior angle theorem

Statement Reason

1. Given

Pg. 3 #15

EBCABD 1.

2. Partition PostulateABEDBEABD 2.

3. Substitution postulateABEDBEEBC 3.

4. A whole is greater than any of its parts

EBCABE 4.

Statement Reason

1. Given

Pg. 3 #16

PTQT 1.

PQTQPT 2.

3. An exterior angle of a triangle is greater than either of its nonadjacent interior angles

PQTSPQ 3.

4. Substitution postulate of inequalities

QPTSPQ 4.

2. Angles opposite congruent sides of a triangle are congruent

Statement Reason

1. Given

Pg. 3 #17

BDAD 1.

ABDA 2.

3. Partition PostulateABCDBCABD 3.

5. Substitution postulate of inequalities

AABC 5.

4. A whole is greater than any of its parts

ABDABC 4.

2. Angles opposite congruent sides of a triangle are congruent

Statement Reason

1. Given

Pg. 3 #18

RTRS 1.

STRS 2.

3. An exterior angle of a triangle is greater than either of its nonadjacent interior angles

SRMT 3.

4. Substitution postulate of inequalities

STRRMT 4.

2. Angles opposite congruent sides of a triangle are congruent

Statement Reason

1. Given

Pg. 3 #19

2 1. ABC

ABC1 2. 2. An exterior angle of a triangle is greater than either of its nonadjacent interior angles

3. Substitution postulate of inequalities

21 3.

Statement Reason

1. GivenRPQPS vertex bisects 1.

QPSRPS 2. 2. An angle bisector divides an angle into two congruent angles

QPSPQT 3. 3. An exterior angle of a triangle is greater than either of its nonadjacent interior angles

4. Substitution postulate of inequalities

RPSPQT 4.