正方形被一条线分成两个三角形。

The square is divided into two ___triangles by a line.

音乐课上，老师教我们如何用小棒敲击三角铁。

In music class, the teacher showed us how to play the ___triangle with a small beater.

当第三人加入后，他们的关系演变成了一个复杂的三角关系。

Their relationship evolved into a complicated ___triangle when a third person joined.

工程师用三角板绘制机械零件的精确角度。

The engineer used ___triangles to draw precise angles for the mechanical parts.