Exterior angle property of a triangle

**Steps to prove the property using this lab are as follows**

**A. Steps to draw a triangle **

- Go to the TOOLS and select the triangle.
- Mark a point A on baseline to draw a triangle ABC.
- Click again on baseline for another point B.
- Click above baseline on the benchmark to mark the point C.

Triangle drawn successfully.

**B. Steps to mark the interior angles and exterior angle**

- Click on point A to mark ∠CAB
- Click on point B to mark ∠ABC,
- Click on point C to mark ∠ACB,
- Click on point D to mark ∠CBD(exterior angle) of triangle ABC.

**C. Measure the values of resultant angles **

- Drag the protractor to measure the value of the interior angles, ∠CAB and ∠ACB.
- Consider AD as a baseline for ∠CAB and line CB for ∠ACB.
- Enter the value of angles ∠CAB and ∠ACB in text box.
- Measure the value of angle ∠CBD i.e. exterior angle from base line AD.
- Enter the value in text box.

**D. Verify the theorem**

- Let us cut and place the interior angles on exterior angle
- Click on point A to cut angle ∠CAB.
- Click on point C to cut angle ∠ACB.

**Observation**

- Click on Next button to see the observation.

We observe that the interior angles completely overlap the exterior angle.

We also observe that **∠CAB +∠ACB = ∠CBD **

Thus, The sum of value of interior angles** ∠CAB and ∠ACB** is equal to the exterior angle **∠CBD.**

Hence exterior angle property of triangle is proved.