Triangle
Calculate triangle properties from sides and angles
How to use Triangle
- 1Enter any three known values of a triangle, such as two sides and an angle.
- 2Choose the solving method if several are possible for your inputs.
- 3Read the missing sides, angles, area, and perimeter.
Solving triangles
Law of sines: a/sin A = b/sin B; Law of cosines: c² = a² + b² - 2ab cos CGiven enough known parts, trigonometry finds the rest; which law to use depends on whether you know sides or angles.
The sum of interior angles is always 180 degrees, a key check that your solved triangle is valid.
Frequently asked questions
Which law should I use?
Use the sine law when you have a side and its opposite angle; use the cosine law for two sides and the included angle.
Why do my angles not add to 180?
Rounding can cause small drift; keep full precision while solving and round only at the end.
Can every set of inputs be solved?
No. Some combinations, like three angles alone, leave the size undetermined.