Final answer:
The two-column proof shows that angle 1 is supplementary to angle 3 using given information, definitions of supplementary angles, and bisected angles to substantiate the reasoning through logical steps.
Step-by-step explanation:
To complete the two-column proof for the conjecture that angle 1 is supplementary to angle 3, we need to fill in the missing statements and reasons. Using the properties of bisected angles and the definition of supplementary angles, we can construct the proof as follows:
∠1 is supplementary to ∠2. - Given
m∠2 + m∠1 = 180° - Definition of Supplementary
BD bisects ∠ABC. - Given
m∠2 = m∠3 - Definition of Angle Bisector
m∠3 + m∠1 = 180° - Substitution (from step 2 and 4)
∠1 is supplementary to ∠3. - Definition of Supplementary (conclusion from step 5)
Each step builds upon the previous information to reach our conclusion that angle 1 is indeed supplementary to angle 3.