Talk:Ideas in Geometry/Instructive examples/Proving the Area of a Trapezoid

I really liked this proof. I though it was clever to make a rectangle out of the two remaining triangles and it works out great. My only suggestion would be to further prove that the two triangles are in fact the same triangle with equal bases. I didn't see anywhere that it says that they are the same but they certainly look the same in the book.

But I think that it would still work out even if they weren't the same length, the algebra would just be much more complicated. ________________________________________________________________________________________________________________________________

I think you all did a good job with this proof by picture. To think about it differently, maybe one consideration can be the way you labeled your trapezoid. I think what is meant by b1 and b2 might be the 2 different bases (the top and bottom parallel lines with different lengths). By starting with this label, you might be able to prove the formula differently.

Overall good job. But, in you're first line of algebra, shouldn't the Area=(b1*h)+(1/2xh)+(1/2xh) rather than multiplying these terms together? However it didn't seem to matter because this was irrelevant to the rest of your proof. Also, I think you could have spent more time explaining the picture and the manipulations in the pictures rather than focusing on and reiterating the algebra that was already shown. Hynes3 21:29, 7 October 2010 (UTC)

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I kind of struggled to understand the part where you figure out the equations. I understand the part where you plug in x, but wasn't the equation you needed to plug in h(b1+x)? how did you get b1-x? when plugging it in. Shouldnt it be h(b1+((b2-b1)/2))im just also confused on how you got to h(2b1+b2-b1). Smoo1244

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I think that you guys did a great job with this proof. At first I was not sure where your variables were coming from; however, once I looked at your picture they made sense. I thought your picture really helped clarify the equations that you were using and it was drawn out very well. Maybe downsize it a little bit so we can see it all on one page? I also liked that you used the two triangles to create a another rectangle. The only real suggestion that I have is that you relate your written description more to your drawing, instead of leaving it up to the reader to do that. I found that I had to read your description a few times before the calculations made sense. Maybe just reference your picture more when you are describing the process. Overall, you guys did a great job of simplifying the problem and making it easier to understand. Good Job! Katelin_Barker90