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Exterior Angle Theorem Calculator

Exterior angle of a triangle calculator. Enter two non-adjacent interior angles to get the exterior angle, explained as their sum—for middle-school geometry.

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Exterior angle = sum of the two non-adjacent interior angles
extB
Angles not adjacent to the exterior
Sum must be <180

📖 Tutorial | Exterior Angle

1. Definition
An exterior angle equals the sum of the two non-adjacent interior angles (Exterior Angle Theorem) and exceeds either.
2. Formula & Notation
ExteriorBetween a side and an extended side
A, BNon-adjacent interior angles
3. Properties & Laws
  • Exterior = sum of non-adjacent interiors;
  • Supplementary to the adjacent interior;
  • Greater than either non-adjacent angle;
  • Exterior angles sum to 360°.
4. Steps
  1. Enter two non-adjacent angles A, B;
  2. Click "Find Exterior";
  3. Or click "Load Example".
5. Worked Examples
Example: non-adjacent angles 50° and 60°.
Solution: exterior = 50+60 = 110°.
6. Common Pitfalls
Use the non-adjacent interior angles;
Supplementary to the adjacent angle;
Their sum must be <180.

❓ FAQ | Exterior Angle

What does an exterior angle equal?
The sum of the two non-adjacent interior angles.
Relation to adjacent angle?
Supplementary, summing to 180°.
Consistent with angle sum?
Yes: 180−adjacent = the other two.
For 50°,60°, exterior?
110°.
Is it larger than non-adjacent angles?
Yes, greater than either.
Sum of three exterior angles?
360°.