triangle前面加the吗

前面可以不加the，例如：

1、The sum of all the angles of a triangle is 180 degrees.三角形内角总和为180度。

2、Its outline roughly forms an equilateral triangle.它的轮廓大致形成一个等边三角形。

3、This area of town is known as the Bermuda Triangle because drinkers can disappear into the pubs and clubs and be lost to the world.城里的这一地区称作“百慕大三角”，因为酒徒进入这里的酒吧和夜总会后一时间消失得无影无踪。