Altitude of a Triangle
Definition of Altitude of a Triangle
Altitude of a Triangle is the perpendicular distance from any of its vertices to the opposite side. (This opposite side of the vertex is called the base of the altitude.)
More about Altitude of a Triangle
 As a triangle has 3 vertices, it has 3 altitudes.
 Altitudes can be used to find the area of the triangle.
Examples of Altitude of a Triangle

In the triangle ABC, AD is the perpendicular distance drawn from vertex A to the side BC. So, AD is the altitude of the triangle.
Video Examples: Altitude of a Triangle  MathHelp.com  Geometry Help
Solved Example on Altitude of a Triangle
Ques: Which of the figures shows an altitude of the triangle drawn?
Choices:
A. Figure 1B. Figure 2
C. Figure 3
D. none of these
Correct Answer: C
Solution:

Step 1: Altitude of a triangle is the perpendicular distance from one of its vertices to its opposite side.
Step 2: The line drawn in Figure 3 from D to EF shows the perpendicular distance between D and EF.
Step 3: So, Figure 3 shows an altitude of the triangle drawn.
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