Quick guide
How to use this calculator
- Choose the calculation mode when the page supports more than one direction.
- Enter the known measurements using the labels and angle units shown.
- Read the primary result first, then use the supporting rows to verify the convention or relationship.
Calculation method
Apply the selected angle relationship
Alternate interior, alternate exterior, and corresponding angles are equal; same-side interior angles sum to 180°.
The calculator validates geometric domains and reports degenerate vectors, impossible measurements, or unsupported ranges explicitly.
Worked example
Worked example
An alternate interior angle to 72° is 72°.
Alternate interior, alternate exterior, and corresponding angles are equal; same-side interior angles sum to 180°.
Supported inputs
Precision and limits
Angle conventions
Positive Cartesian rotations are counterclockwise. North-referenced azimuths run clockwise. Unoriented line and plane calculators return the smaller acute or right angle; directed vector and dihedral tools can return up to 180°.
Numerical range
Inputs may be zero or have absolute magnitude from 1e-100 through 1e100. General angle magnitudes are limited to 1,000,000,000 degrees so periodic reduction remains meaningful in double-precision arithmetic.
Precision
Calculations use finite double-precision arithmetic and normally display 12 significant digits. Results are numerical unless the page explicitly displays a fixed geometric identity.
Calculator-specific rule
These relationships require the two crossed lines to be parallel.