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well they are the same shape for a start and corresponding sides are in the same proportion
Ok, I know that they are the same shape, and I know how to cross multiply, but how do you get from the fact that they are the same shape, to that they are similar using proportions? If you can draw how, I would understand it better. Thanks!
the small triangle is similar to the large one corresponding angles are the same and sides in same ratio
How do you write that ratio?
triangles ABC and ADE are similar so AD = DE = AE -- -- -- AB BC AC so knowing length of 3 sides you can find one side
??? So, so if you are just given the shape, and the sides, how do you prove that they are similar?
this is true for all similar polygons the areas can also be found using (in above example): AD|^2 / AB^2 = area ADE / area ABC
triangles are proved to be similar if 2 corresponding angles are equal (therefore third is equal) or corresponding sides are in same proportion
I get the first reason, but not the second. What about other shapes (rhombi, squares, etc)?
a good site to explain is http://library.thinkquest.org/20991/geo/spoly.html
its equally true for all other polygons
I feel a little bad for you having to explain this to a dumb person! Thanks for your help though!!
it works both ways - if shape is same then corresponding sides are in same proportion and vice versa
thats ok - yw
It's starting to make sense now!!