Triangle Identities

You might like to read our page on Trigonometry first!

Triangle Identities

The triangle identities are equations that are true for all triangles (they don't need to have a right angle). For the identities involving right angles triangles see Trigonometric Identities.


Law of Sines

The Law of Sines (also known as The Sine Rule) is:

Law of Sines

it can also be this way around:

Law of Sines


Law of Cosines

The Law of Cosines (also known as The Cosine Rule) is an extension of the Pythagorean Theorem to any triangle:

law of cosines

which can also be re-arranged to:

law of cosines alt

Law of Tangents

The Law of Tangents is:

law of tangents