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Re: help
Posted:
Jan 17, 2008 8:26 AM


"Tony Welscher" <389removethisnow@insightbb.com> wrote in message news:XeGdnVr26tL0MXXYnZ2dnUVZ_oytnZ2d@insightbb.com... > > First let me say that if this is too simple for this site I am sorry. I'm > just a old timer that is trying to maximize my cuts on a sheet of > plywood. > > Trapezoid Question > I know the base measurement and the angles of the trapezoid. > I need the sides and the top to be equal > Is there a formula that I can input the base length and angles to find the > 3 equal sides? > > The reverse to this question > I know the equal length of the 2 sides and the top. I know the degrees of > the angles > Is there a formula that will tell what the base needs to be. > > Thanks for your help > >  > Tony Welscher
Solving the reverse question is easier. If you drop perpendiculars from the ends of the top to the base, you end up with a rectangle with a triangle on each side. Let S be the length of your sides and top. The length of the side of one triangle (T) which is on the base (B) of the trapezoid would be:
T = S * sin(A  90)
Since B = S + 2 * T,
B = S + 2 * S * sin(A  90)
To solve the first question, solve the equation for S.
B = S * ( 1 + 2 * sin (A  90))
S = B / ( 1 + 2 * sin(A  90))
Paul



