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.