Cynthia is writing a proof of the theorem stated below.
Theorem: The sum of interior angles of a triangle is 180°.
She first drew the figure shown below.

Question

Cynthia is writing a proof of the theorem stated below.
Theorem: The sum of interior angles of a triangle is 180°. 
She first drew the figure shown below.

anonymous · Answer

attachment

anonymous · Answer

Which theorem will she most likely use in the proof?

 Vertical angles are congruent.

 Alternate Interior Angles formed by parallel lines and their transversal are complementary.

 If two angles form a straight angle, then they are supplementary.

 Corresponding angles formed by parallel lines and their transversal are supplementary.

anonymous · Answer

If two angles form a straight angle, then they are supplementary.

anonymous · Answer

so D?

anonymous · Answer

C i mean?

anonymous · Answer

yeah.  it's not a very well written question though.

anonymous · Answer

because she actually uses more than one of the above theorems to "draw the figure below".  But yeah, option C is the crucial one to apply once you have the drawing.

anonymous · Answer

oh okay thanks

anonymous · Answer

oh wait, I miss read one of them.  the question is ok.  she only uses theorem "c".

anonymous · Answer

im thinking the answer is B

anonymous · Answer

bcuz i found a question exactly the same just with one different answer...