triangle law

例句：

1. 1. The triangle law states that the sum of the interior angles of a triangle is always 180 degrees.
   三角形法则指出，三角形内角和总是180度。
2. 2. In trigonometry, the triangle law is used to find the length of a side in a right-angled triangle.
   在三角学中，三角形法则用于计算直角三角形边长的长度。
3. 3. The triangle law is also important in geometry and engineering for calculating the area of a triangle.
   三角形法则在几何学和工程学中也非常重要，用于计算三角形的面积。