Lines and Angles Calculator
Solve angle problems from Lines and Angles: complements and supplements, the eight angles where a transversal cuts parallel lines, a triangle's third and exterior angles, angles in a ratio, and polygon angle sums.
About the Lines and Angles Calculator
When a transversal cuts two parallel lines it makes eight angles of only two sizes: corresponding angles, alternate interior and exterior angles, and vertically opposite angles are equal, while co-interior angles (on the same side, between the lines) add to 180°.
In any triangle the angles add to 180°, and an exterior angle equals the sum of the two interior opposite angles.
The formula
A + B + C = 180°; exterior angle = sum of interior opposite angles; polygon: (n − 2) × 180°
Worked example
Example: The eight angles = 70° and 110°
- Inputs: I want: All eight angles: parallel lines cut by a transversal; Angle (degrees): 70.
- Formula: A + B + C = 180°; exterior angle = sum of interior opposite angles; polygon: (n − 2) × 180°
- Linear pair: 180° − angle: 180° − 70° = 110°
- Result: The eight angles = 70° and 110°
- Corresponding angles: equal
- Alternate interior angles: equal
- Co-interior angles: add to 180° (70° + 110°)
Questions people ask
What's the difference between alternate and corresponding angles?
Corresponding angles sit in the same position at each crossing (both top-left, say). Alternate angles are on opposite sides of the transversal, one at each crossing.
Can a triangle have two obtuse angles?
No. Two obtuse angles already add to more than 180°.