# Triangle calculator

The following formulas are right in equations:

Sine rule:

a / b = sin alpha / sin beta

Cosine rule:

a^2=b^2+c^2-2bc cos alpha

A triangle has three sides and three corners.

In every corner, there is an interior angle, i.e. the angle between the sides ending at that corner.

The sum of all interior angles of a triangle is always 180 degrees.

A triangle can also be determined by three other values. But for example, if you got two sides and the height on one side, there is more than one possible triangle with those lengths.

The sides and angles can be calculated by using sine and cosine. The following formulae hold:

a/sin(alpha)=b/sin(beta) (sine rule)

Furthermore, for three sides a,b,c and angle alpha opposing of a:

a^2=b^2+c^2-2bc cos alpha (cosine rule)

For further information, move the mouse above the words below and the corresponding line will be marked on the triangle.

Side a Side b Side c

Angle alpha Angle beta Angle gamma

height on a height on b height on c

median line on a median line on b median line on c

angle bisector of alpha angle bisector of beta angle bisector of gamma

area