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Home >> Triangle >> Adjacent Interior Angle of Triangle >> Examples

Adjacent Interior Angle of Triangle : Solved Examples

Properties Types / Classification Perimeter of Equilateral Triangle Median of Triangle Interior of a Triangle
Exterior of a Triangle Altitude of a Triangle Interior Angles of Triangle Exterior Angles of Triangle Interior Opposite Angles of Triangle
Adjacent Interior Angle of Triangle Congruent Triangles Area of Triangle Area of Triangle by Heron's Formula Construction of Triangle (compass)



What can you say about the sum of an exterior angle of a triangle and its adjacent angle ?
Look at the following diagram:



Interior and Exterior Angles are marked as , , &

You can also observe that:
∠ 1 = Exterior angle
∠ 2 = Adjacent Interior Angle to Exterior ∠ 1

Now, you can notice that ∠ 1 & ∠ 2
Are on same Vertex C
Share common Arm AC
Therefore, ∠ 1 & ∠ 2 are Adjacent Angles………………(Statement 1)
Also, ∠ 1 & ∠ 2 are on the same straight line BC……...(Statement 2)

So, from Statement 1 and Statement 2; we get
∠ 1 & ∠ 2 forms a linear pair.

Or we can also say that "Exterior angle of a triangle and its adjacent angle forms a Linear Pair".

Hence, sum of an exterior angle of a triangle and its adjacent angle is equals to 180

Related Question Examples

  • What can you say about the sum of an exterior angle of a triangle and its adjacent angle ?
  • Find measure of ∠ CBD in the following figure:
  • Find the measure of adjacent interior angle of a triangle, whose exterior angles is 80°
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