Monday，2022.1.9
New Words：
triangle [ˈtraɪæŋɡl] n. 三角形;三角形物体
Sample Sentences：
Cut the sandwiches into triangles.
The angles of a triangle total 180.
The sum of all the angles of a triangle is 180 degrees.
sum [sʌm] n. 和，总和，总数;全部，一切
angle [ˈæŋɡl] n. 角;斜角