when two parallel lines are intersected by a transversal,

i) alternate interior angles are equal

ii) corresponding angles are equal

iii) same side interior angles are supplementary

how to prove the above?

(I found some proofs in the internet. But they can not be accepted. Because they use theorem ( i ) to prove theorem ( ii ) and again theorem ( ii ) to prove theorem ( i ). So I want to find an independent proof.)

Thank you

## Answers (1)

to prove the first one, use the fact that all triangles have 180 degrees. take a line and make it go through one of the intersections, then take a line parallel to that line and have it go through the other intersection. you now have your triangles, so get movin'. and yes you can prove 2 with 1