Trigonometry
Law of Cosines (angle)
Angle opposite c from three sides.
Formula
Formula
C = acos(a2+b2−c22ab)
Variables
| Symbol | Definition | Type & range | Units | Role |
|---|---|---|---|---|
| a, b, c | three sides | real number (ℝ) | — | input |
| C | angle opposite c | real number (ℝ) | — | input |
Try it yourself
Interactive calculator
Worked examples
Example 1
Givena = 5, b = 7, c = 8
Result81.7867893
Example 2
Givena = 3, b = 4, c = 5
Result90