Statement
Reason
1. Let points A, B, and C form a
triangle.
given
2. Let be a line passing
through B, parallel to ,
with angles as labeled.
defining a parallel line and labeling angles
3.
4. , and
.
Congruent angles have equal measures.
5.
angle addition and definition of a straight angle
6.
substitution
What is the missing step in this proof?
Statement: , and .
Reason: Alternate Interior Angles Theorem
Statement: is parallel to .
Reason: is a transversal cutting and .
Statement: , and .
Reason: Alternate Interior Angles Theorem
Statement: , and .
Reason: and , and and are pairs of supplementary angles.