A classmate said that line AB is parallel to line DC, based on the diagram (below). Explain their error.

Question

anonymous · Answer

|dw:1415220455086:dw|

Not sure why they are not parallel: Help please? @MAli13chineta

anonymous · Answer

http://openstudy.com/users/ganeshie8#/updates/5242ca66e4b0a03c277f5db5

anonymous · Answer

Could you simplify that please???? It's chaos to me....

anonymous · Answer

@MAli13chineta

anonymous · Answer

The actual error was in applying the alternate interior angles theorem incorrectly. The student arrived at the conclusion that AB || CD because, he thought WZ adn XY are parallel, but they're not given as parallel. He **assumed** them to be parallel, which is a serious offense in geometry proofs.

anonymous · Answer

Once he made that error, ∠WZY≅∠XYC by corresponding angles postulate. then by applying   alternate interior angles theorem  , he concluded that AB || CD

anonymous · Answer

also observe that, we're given  ∠AWZ≅∠XYC.
so its very easy to get fooled !

anonymous · Answer

ok thanks. I have one more question I'm going to post. :)

anonymous · Answer

thats what ganeshine said just read the last 6 comments

anonymous · Answer

ok :) bye
 medal plz