三角函数

例句：

1. 1. The function of a triangle is to measure the length of its sides.
   三角形的功能是测量其边长。
2. 2. The area of a triangle is calculated using the formula s = (a + b + c) / 2, where a, b, and c are the lengths of its sides.
   三角形的面积通过公式计算，其中a、b和c分别是其边长。
3. 3. In geometry, the angles of a triangle are measured in degrees.
   在几何学中，三角形的角度以度为单位测量。