Law of Cosines Side
The law of cosines extends the right-triangle relation to any included angle. The required angle lies between the two known sides.
Law of Cosines Side
Triangles · 3 inputs
How to use this calculator
- Enter first side in cm.
- Enter second side in cm.
- Enter included angle in degrees.
- Select Calculate and keep the output unit with the answer.
Before you use the answer
Start with a dimensioned sketch and label the units beside every measurement. Distinguish the outer edge from an internal opening, and distinguish a radius from a diameter. A geometric model is most useful when the shape actually matches the assumptions in the formula.
Using an angle opposite one of the entered sides gives a different problem and an incorrect result here.
Does it save my inputs?
No calculation history is stored by this website. The calculator works locally in your browser. See the privacy policy for hosting and contact details.
Why might a result be approximate?
Measurement uncertainty, ideal-model assumptions and floating-point rounding can all matter. Displaying more digits does not improve the original measurement.
Related calculations
Parallelogram Area
Sliding a corner triangle to the other side turns a parallelogram into a rectangle without changing its area.
Open calculator ↗Trapezoid Area
A trapezoid's average parallel width multiplied by its perpendicular height gives the enclosed area.
Open calculator ↗Rhombus Area
The perpendicular diagonals of a rhombus split it into four right triangles.
Open calculator ↗