Median and Altitude of Triangle


 
 
Concept Explanation
 

Median and Altitude of Triangle

Median and altitude of triangle: A median is a line segment drawn from the vertex of a triangle to the midpoint of the opposite side of triangle. As in a triangle there are three vertices and three sides, therefore there are three medians in each triangle. From each vertex we can draw a line joining the midpoint of the opposite side of the triangle. It divides the opposite side into two equal line segments. In the figure AE is a median as E is the midpoint of the side BC. Thus BE = EC

Altitude: An altitude is a perpendicular line segment drawn from a vertex of a triangle to the opposite side. There are three altitudes in a triangle as there are three vertices and three side. In the figure AD is the altitude from vertex A. AD is perpendicular to BC.

Theorem: Show that median of a triangle divides it into two triangles of equal area.

Given: A triangle ABC with AE as the median

To Prove: ar (large Delta ABE) = ar (large Delta ABE)

Construction:  Draw AD large perp BC

Proof: large Area ;of; a; triangle; =frac{1}{2};X ;base;X; height

large ar (Delta ABE); =frac{1}{2};X ;BE;X; AD            ..........(1)

large ar (Delta AEC); =frac{1}{2};X ;EC;X; AD              ........(2)

As AE is a median    large Rightarrow BE = EC

From Eq (1) and (2)   ar (large Delta ABE) = ar (large Delta ABE)

Hence Proved.

ILLUSTRATION: In the figure E is the mid point of the median AD of triangle ABC. Prove that:

large ar(Delta BDE)=frac{1}{4} ar (Delta ABC)

Solution:  It is given that AD is the median

we know that the median divides the triangle into two triangles of equal area

large therefore ar(Delta ABD)=frac{1}{2} ar (Delta ABC)      .....(1)

Also E is the midpoint of AD. Therefore AE is the median of triangle ABD

large therefore ar(Delta BDE)=frac{1}{2} ar (Delta ABD)

Using equation 1

large Rightarrow ar(Delta BDE)=frac{1}{2} ;X; frac{1}{2}ar (Delta ABC)

large Rightarrow ar(Delta BDE)=frac{1}{4}ar (Delta ABC)

Sample Questions
(More Questions for each concept available in Login)
Question : 1

The area of a triangle is 72 square units. Find the length of the altitude if the length of the base is 9 units.

Right Option : A
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Explanation
Question : 2

The area of a triangle is 50 square units. The length of the altitude is _______ if the length of the base is 10 units.

Right Option : C
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Explanation
Question : 3

If ABC is a triangle and AD is its median lying on the side BC, then

Right Option : B
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Explanation
 
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