Median in a triangle

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Median in a triangle

A median in a triangle is a line segment that extends from a vertex to the midpoint of the opposite side, dividing it into two equal parts.

Additional properties:

  1. In every triangle, it is possible to draw 3 medians.
  2. All 3 medians intersect at one point.
  3. The median to a side in a triangle creates 2 triangles of equal area.
  4. In an equilateral triangle - the median is also a height and an angle bisector.
  5. In an isosceles triangle - the median from the vertex angle is also a height and an angle bisector.
  6. In a right triangle - the median to the hypotenuse equals half the hypotenuse.

Diagram of triangle ABC showing medians AD, BE, and CF intersecting at the centroid. The centroid divides each median into a 2:1 ratio, illustrating triangle centroid properties.

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Test yourself on parts of a triangle!

Is DE side in one of the triangles?
AAABBBCCCDDDEEE

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Median in a triangle

In this article, we will learn everything you need to know about medians in a triangle! Don't worry, the material about medians in a triangle is both easy and straightforward to understand.

Define a median in a triangle?

A median in a triangle is a line segment that extends from a vertex to the midpoint of the opposite side, dividing it into two equal parts.
Remember that "median" in real life represents the middle point, and similarly here it divides the side in the middle!

We can observe this in the following drawing:

Diagram of a triangle ABC with a median AD drawn from vertex A to the midpoint D of side BC, illustrating geometric properties of medians.

In triangle ABCABC
ADAD is a median - it extends from the vertex AA and divides the opposite side CBCB into two
equal parts: CD=BDCD=BD

Additional Properties of a Median in a Triangle:

  1. In every triangle, it is possible to draw 3 medians.
  2. All 3 medians intersect at one point.
  3. The median to a side of a triangle creates 2 triangles of equal area.


You can observe this below:

Diagram of triangle ABC showing medians AD, BE, and CF intersecting at the centroid. The centroid divides each median into a 2:1 ratio, illustrating triangle centroid properties.


Since there are 3 vertices in a triangle, there can be 3 medians.
Each median extends from a vertex to the opposite side and bisects it.
All medians intersect at one point.


Reminder:
How do we calculate the area of a triangle?

heightcorresponding side to height2height*corresponding~side~to~height \over 2

If we take for example the triangle ABCABC and want to calculate its area when:
ADAD height = 66
BC=8 BC = 8

Diagram of triangle ABC with median AD labeled. The length of median AD is shown as 6 units, and segment BD is labeled as 4 units, highlighting the geometric properties of a triangle's median.



We can deduce that the area of triangle ABCABC is:
682=24\frac{6*8}{2}=24
Now if we draw the median ADAD we can observe that the two triangles it creates are equal in area.
The side is divided in the middle thus it is identical in both triangles and the height is identical.
Therefore, the area of each created triangle is identical and will be equal to half the area of triangle ABCABC

642=12\frac{6*4}{2}=12

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3 important statements about medians:

  1. In an equilateral triangle - the median is also a height and an angle bisector.
    As shown in the figure:

    ADAD is a height to side CBCB
    and also a median to side CBCB (divides it into two equal parts)
    as well as an angle bisector

Diagram of an isosceles triangle with a median intersecting the base at a right angle. The median forms a perpendicular bisector, and the top angle is highlighted in purple.

AA

  1. In an isosceles triangle - the median drawn from the vertex angle is also a height and an angle bisector.
    Let's observe this in the figure below:
In an isosceles triangle - the median drawn from the vertex angle is also a height and an angle bisector.

ADAD is a median drawn from vertex angle AA.
It is also a height to side CBCB, as well as a median to CBCB, in addition to bisecting the vertex angle AA.


3. In a right triangle - the median to the hypotenuse equals half the hypotenuse.

We can observe this in the figure below:

In a right triangle - the median to the hypotenuse equals half the hypotenuse.

Triangle ABCABC is a right triangle.
CDCD is the median to the hypotenuse and equals half of the hypotenuse.
That is
CD=AD=DBCD=AD=DB

Exercise:

Given:

CDCD is a median in triangle ABCABC
CECE is a median in triangle ACDACD

AB=14AB=14

Diagram of a triangle with medians AD and CE drawn in orange and purple, intersecting at a single point inside the triangle. The vertices are labeled A, B, and C, while the midpoints of the sides are labeled D and E.

  1. Calculate the length of segment AEAE.
  2. Determine the area of triangle ECDECD if it is known that the area of triangle ACEACE is 66?
  3. Based on your answer in part b, determine the area of triangle DCBDCB

Solution:

  1. Let's mark the given information in the drawing.
Diagram of a triangle labeled A, B, and C, with medians AD (orange) and CE (purple). The length of CE is marked as 3.5. A green arc labeled 14 spans from vertex A to vertex B, highlighting the angle subtended by side AB.

Given that – AB=14AB =14
Since CDCD is a median,
AD=DB=7AD=DB=7
due to the fact that the median bisects the side at its midpoint.
Given that CECE is also a median.
Therefore AE=ED=3.5AE=ED=3.5.

2. Given that the area of triangle ACEACE is 66
The area of triangle ECDECD
must also be 66. A median divides the triangle into two triangles of equal area.

3. The area of triangle DCBDCB must be equal to the area of triangle ACD ACD.

Triangle ACDACD consists of two triangles with equal areas that sum up to 1212.
Therefore, the area of triangle DCBDCB is 1212.

Do you know what the answer is?

Examples with solutions for Parts of a Triangle

Exercise #1

Is DE side in one of the triangles?
AAABBBCCCDDDEEE

Video Solution

Step-by-Step Solution

Since line segment DE does not correspond to a full side of any of the triangles present within the given geometry, we conclude that the statement “DE is a side in one of the triangles” is Not true.

Answer

Not true

Exercise #2

Determine the type of angle given.

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Examine the diagram presented.
  • Step 2: Identify any familiar angle formations or configurations.
  • Step 3: Use knowledge of angles to classify the type shown.
  • Step 4: Determine the correct response from available options.

Observing the diagram:

The diagram includes two lines, one horizontal and the other vertical, extending fully. This horizontal extent along with the linear continuation suggests it forms an angle at the intersection with 180180^\circ. This indicates a straight angle.

We classify straight angles because an angle formed by two lines directly facing opposite directions is known to measure 180180^\circ. This diagrammatic representation aligns perfectly to confirm it calculates and visually shows a straight angle.

Thus, by recognizing these details within the diagram, we confirm the type of angle as Straight.

Answer

Right

Exercise #3

Determine the type of angle given.

Video Solution

Step-by-Step Solution

The problem involves classifying the angle represented visually, which looks like a semicircle with a central axis drawn. This indicates an angle that spans half a complete circle.

A complete circle measures 360360^\circ, so half of it, represented by a semicircle, measures half of 360360^\circ, which is 180180^\circ.

The four primary classifications for angles are:

  • Acute: Less than 9090^\circ
  • Right: Exactly 9090^\circ
  • Obtuse: Greater than 9090^\circ but less than 180180^\circ
  • Straight: Exactly 180180^\circ

Since the angle measures exactly 180180^\circ, it is classified as a straight angle.

Therefore, the type of angle given is Straight.

Answer

Straight

Exercise #4

Is the straight line in the figure the height of the triangle?

Video Solution

Step-by-Step Solution

The task is to determine whether the line shown in the diagram serves as the height of the triangle. For a line to be considered the height (or altitude) of a triangle, it needs to be a perpendicular segment from a vertex to the line that contains the opposite side, often referred to as the base.

Let's analyze the diagram:

  • The triangle is described by its vertices, forming a shape, and one side is the base. There's a line drawn from one vertex directed toward the opposite side.
  • To be the height, this line must be perpendicular to the side it meets (the base).
  • Though the figure does not explicitly show perpendicularity with a right angle mark, the line appears as a straight, direct connection from the vertex to the base. This is typically indicative of it being a height.
  • Assuming typical geometric conventions and the common depiction of heights in diagrams, the line shows properties consistent with being perpendicular to the opposite side, thereby functioning as the height.

Based on the analysis, the line is indeed the height of the triangle. Thus, the answer is Yes.

Therefore, the solution to the problem is Yes.

Answer

Yes

Exercise #5

Is the straight line in the figure the height of the triangle?

Video Solution

Step-by-Step Solution

To determine if the straight line in the figure is the height of the triangle, we must verify the following:

  • The line segment must extend from a vertex of the triangle and be perpendicular to the opposite side (or its extension).

In examining the figure provided, we notice that the triangle is formed by vertices at points A,B, A, B, and C C . Let's assume the base is the line segment BC \overline{BC} .

The line in question extends from a vertex A A and appears to intersect the base BC BC at a right angle.

  • Since it is extending from vertex to the opposite side and forming a right angle with it, this line meets the definition of an altitude.

Therefore, the line in the figure is indeed the height of the triangle. By confirming the perpendicular relationship, we determine that this geometric feature correctly describes an altitude.

Yes, the straight line in the figure is the height of the triangle.

Answer

Yes

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