Thread: Co interior, alternate and corresponding angles.

Hi,

In grade 8 we are learning of the above angles. I understand it briefly e.g what an alternate angle is...

What I don't understand is the reasons.

E.G
She would give us a pic like this:

Google Image Result for http://www.mathsteacher.com.au/year8/ch09_geometry/01_geom/Image13351.gif



But our pic would have the degree of one angle. e.g y= 60

She would then tell us to work out x. That is easy. 180-60=x
But then she tells us to give a reason and she says the reason will be: adjacent angles on a straight line. What I don't get, are the reasons for co interior and corresponding angles.

E.G She would give us a pic like this Google Image Result for http://www.mathleague.com/help/geometry/IMG00046.gif

But give us the value of C D and B and say work out A. She would then say. Give a reason for why you say that. Also, how would I work that out? I know the answer in my head, but need to show working out.
Help would be appreciated!

Thanks.

Hi jesseE fantasma,
Google parallel lines and transversals for angle definitions and properties.If you can't find a proof for a theorem like alternate interior angles are equal repost and I will give you one.In geometry you learn theorems and learned you can use them without proof to solve a problem


bjh