ow i just passed by.. and i saw this and maybe i can help.. try to see this one.. hehe.. [img]http://i12.tinypic.com/5zgd1tc.gif[/img] i stated that tha angels in the middle is equal because of law on vertical angles and also it is obvious that one angle is 90degrees.. anyway.. let's assume that the 2 vertical angles is a variable x.. FYI: Angles in a triangles sum up to 180. so [b]90 + x(the vertical angles) + y(remaining angles) = 180[/b] so therefore the two triangles are equal.. why?? because first 90 they both have ninety.. and x is the same.. so it means the remaining y should be equal.. same as the AA Postulate said above. next.. we said its equal ayt?? so we can apply ratio and proportion in this kind of problem.. that is why.. we can say. base1/base2 = height1/height2 that is why. 50(8)/10 = 400/10 = 40m hope you get my point.. ps: sorry for i messed up your image..