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Peter Chang
Posts:
8
From:
new zealand
Registered:
7/5/08


Re: Trapazoid geometry
Posted:
Jul 8, 2008 5:37 AM


Suppose that AB//CD, the other two sides that are not parallel are BC and AD, Let alpha and beta denote the angle <ADC and <BCD. Let a , b and h denote AB, CD and the trapezoid altitude.
Draw line BE // AD.
In triangle BCE, h/tan(alpha) + h/tan(beta) = b  a
So h = (b  a)/[1/tan(alpha) + 1/tan(beta)] = (b  a)tan(alpha)tan(beta)/[tan(alpha) + tan(beta)]
http://www.idealmath.com



