# Law of Tangents

## Triangles and law of tangents

The "Law of Tangents" can be used to calculate the angles or sides of a triangle.

The "Law of Tangents" can be expressed as

*(a + b) / (a - b) = tan 1/2 (A + B) / tan 1/2 (A - B) (1)*

*where *

*a, b and c = length of sides in triangle (m, ft ...)*

*A, B and C = angles in the triangle (degrees)*

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