一、掌握三角形高的概念从三角形的一个顶点向它的对边所在的直线作垂线,顶点与垂足之间的线段叫做三角形的高.如图1,AD⊥BC,则线段AD是△ABC的一条高.温馨提示:三角形的高是一条线段,其表示方法有两种:(1)用垂直符号;(2)用含90°的角表示.例1有下列说法:(1)三角形的高就是三角形的顶点到对边的距离,它是一个正数;(2)三角形的高是一条垂线;(3)直角三角形的高与直角边重合:(4)三角形的高是顶点到对边所在直线的垂线段. First, the concept of mastered triangle High from the vertex of a triangle to the opposite side of the line for vertical, the vertex and foot drop between the line is called the triangle height .As shown in Figure 1, AD ⊥ BC, then the line AD is △ ABC a high. Reminder: The triangle is a high line segment, which means there are two ways: (1) with a vertical symbol; (2) with the angle of 90. The following example 1 cases (1) triangle (2) The height of the triangle is a vertical line; (3) The height of the right triangle coincides with the right-angle edge: (4) The height of the triangle is the vertex to the right On the edge of the vertical line segment.