# Probably Stupid, but trouble with Proofs.

• Nov 6th 2008, 10:03 AM
Savior_Self
Probably Stupid, but trouble with Proofs.
it's a two-column proof problem...
says prove Line AD is congruent with line BC.

http://img383.imageshack.us/img383/8...elagramym0.jpg
Statement | Proof
AD parallel with BC | given
DC parallel AB | given
??

using the given,which angles are congruent considering the two parallel lines are cut by the transversal? and what is the specific term for that anyway?

Thanks for any help, guys.
• Nov 6th 2008, 12:20 PM
masters
Quote:

Originally Posted by Savior_Self
it's a two-column proof problem...
says

Prove: $\displaystyle \overline{AD}\cong \overline{CB}$

http://img383.imageshack.us/img383/8...elagramym0.jpg

STATEMENTS...............................REASONS

(1) $\displaystyle \overline{AD}\parallel\overline{BC}\ \ and \ \ \overline{DC}\parallel\overline{AB}$...............GIVEN

(2) $\displaystyle \angle ACD \cong \angle CAB \ \ and \ \ \angle DAC \cong \angle BCA$.............If two parallel lines are cut by a transversal, alternate interior angles are congruent.

(3) $\displaystyle \overline{AC}\cong\overline{AC}$........Reflexive property of congruence.

(4) $\displaystyle \triangle ADC \cong \triangle CBA$..........ASA

(5) $\displaystyle \overline{AD}\cong\overline{CB}$..........CPCTC

Quote:

Originally Posted by Savior_Self
Using the given,which angles are congruent considering the two parallel lines are cut by the transversal? and what is the specific term for that anyway?

Thanks for any help, guys.

I guess you're referring to step 2 above.
• Nov 6th 2008, 01:46 PM
Savior_Self
Ah, now I understand. Much thanks.