三さん角かく定じょう規ぎ

noun

set square; triangle (drafting)

A flat triangular tool used in mechanical drawing and geometry to draw straight lines and measure angles; typically a right-angled triangle with one 90° and two 45° angles, or 90°/60°/30°.

• 製せい図ずの授じゅ業ぎょうでは三さん角かく定じょう規ぎとコンパスを使つかいます。

  In drafting class, we use a set square and a compass.

• 三さん角