| 摘要 |
A transparent plastic template permits an angle to be conveniently trisected with a pencil and straight edge. The template has thr ee holes equally spaced apart along a hypothetical line, a central hole and a pair of outer holes. A circle is centered about one of the outer holes, and has a radius equal to one-half the spacing between the outer holes. A line is defined on the template, perpendicular to the hypothetical line and intersecting the midpoi nt of the hypothetical line. The template is manually positioned on the angle with its line intersecting the vertex of the angle. Simultaneously, the circle is positioned so one arm of the angle forms a tangent, and the opposing outer hole is positioned on the other arm of the angle. The central hole and the hole surrounded by the circle are then positioned to mark a pair of trisecting lines through the vertex.
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