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Could someonehelp me to understand these sentences:

A “basic triangle at $q$” will mean a triangle which has the sides adjacent to the vertex $q$ of equal length and an angle at $q$ of measure $30$. The height (or bisector) at $q$ will be used to orient the triangle vertically or with slope $-1$.

Thanks ahead:)

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A basic triangle at $q$ is an isosceles triangle with one vertex at the point $q$. Two equal sides of the triangle form the angle at $q$, and that angle is a 30 degree angle. If you draw a perpendicular from the point $q$ to the opposite side of the triangle, thereby bisecting the angle at vertex $q$, this perpendicular either is vertical or has a slope of $-1$, meaning that it runs diagonally from upper left to lower right at a 45 degree angle to the horizontal. Here's a not-very-good picture:

enter image description here

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Thanks; could you draw a picture for me to understand? – Paul May 12 '12 at 8:24
@John: Does that help? – Brian M. Scott May 12 '12 at 8:28
@Brain:It is very useful. Thanks very much. I haven't see you for several months:) – Paul May 14 '12 at 1:39

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