Law of Cosines Calculator
Third side of a triangle from two sides and the included angle.
Compare Your Options And Get Clear Answers
Third side of a triangle from two sides and the included angle.
Law of Cosines Estimator
Enter your numbers below for an instant estimate.
How It Works
Key concepts behind this calculator
Enter Values
Fill in each field with your own numbers.
Calculate
Results update as you change the inputs.
Review
Read the breakdown and the explanation.
Adjust
Change values to compare scenarios.
Law Quick Guide
Typical values for reference.
| Side a | Side b | Included angle C (deg) | Side c |
|---|---|---|---|
| 7 | 9 | 50 | 7.00 |
| 5 | 12 | 90 | 13.0 |
| 10 | 10 | 60 | 10.00 |
| 3 | 8 | 30 | 5.61 |
| Rule of Thumb | Check inputs | Use as a guide | Round sensibly |
Law of Cosines Calculator FAQ
Answers to common questions about this calculator.
It uses the formula shown with your inputs. Real conditions vary, so treat it as a guide.
c = sqrt(a^2 + b^2 – 2ab cos C)
It is an estimate based on the inputs you enter. Check real quotes, labels or official guidance for important decisions.
Yes. Replace each input with your own figures and the result updates instantly.