Geometry & Measurement Calculators
Triangle Side Calculator
Solve a missing triangle side with the Law of Cosines or the Law of Sines.
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What is Triangle Side?
The Law of Cosines (c² = a² + b² − 2ab·cos(C)) solves the third side from two sides and the angle between them. The Law of Sines solves unknown sides from a known side and its opposite angle.
How it works
We detect which law applies to your inputs, solve for the missing side, and then derive the remaining angles and area from the completed triangle.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
Nothing is uploaded — every tool in this category runs entirely in your browser.