欧几里得在《几何原本》中提出的公理体系至今仍在教学中使用。

The axiomatic system developed by ___Euclid is still taught in geometry classes today.

在欧几里得几何中，三角形的内角和总是180度。

In ___Euclidean geometry, the sum of angles in a triangle is always 180 degrees.