reasons (to use in proofs)

Question 1

definition of midpoint

Answer 1

if M is on AB such that M is the midpoint of AB, then AM≅MB

Question 2

Reflexive property of congruence/equality

Answer 2

anything is congruent or = to itself (use when 2 triangles share the same side or angle)

Question 3

subsitution

Answer 3

If A=B and A =12, the 12 = B

Question 4

transitive property of congruence/equality

Answer 4

if AB≅CD and CD≅EF, then AB≅EF (for sides)
If <A <B and <B ≅<C, then <A ≅<C

Question 5

complementary angles

Answer 5

if <A and <B are complementry, then m<A + m<B = 90

Question 6

supplementary angles

Answer 6

if <A and <B are supplementary, then m<A + m<B = 90

Question 7

sum of angles

Answer 7

m<ABC + m<CBD = m<ABD
(you need a picture to understand this better)

Question 8

sum of segments

Answer 8

AB + BC = AC

Question 9

definition of congruent angles

Answer 9

if m<A = m<B, then <A ≅ <B (and vice versa)

Question 10

definition fo congruent segments

Answer 10

if AB = CD then AB≅CD (and vice versa)

Question 11

definition of Angle Bisector

Answer 11

if BD bisects <ABC, then <ABD ≅ <DBC

Question 12

straight line/definition of a linear pair

Answer 12

angles that make up a straight line are supplementary

Question 13

symmetric prop. of ≅ / =

Answer 13

if a = b, then b=a
if a≅b, then b≅a