How it is calculated
Pythagoras: c² = a² + b² Law of cosines: c² = a² + b² − 2ab·cos C Law of sines: a / sin A = b / sin B = c / sin C A + B + C = 180°Area by Heron’s formula: √(s(s−a)(s−b)(s−c)) where s is half the perimeter.
Worked example
A right triangle with legs 3 and 4: hypotenuse = √(9 + 16) = 5, angles 36.87° and 53.13°, area 6.
Frequently asked questions
How do I know a triangle is right-angled?
If the square of the longest side equals the sum of the squares of the other two.
Can there be two solutions?
With two sides and a non-included angle there may be two; that is why the calculator asks for the included angle.
What unit are angles in?
Degrees (180° = π radians).