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Triangle Side Calculator

Find the opposite side with the cosine rule. All lengths must use the same unit.

Free to useNo sign-upRuns in your browser
Enter your details

Enter the inputs, then select Calculate.

Your result
Enter your details

Result will appear here

How Triangle Side Calculator works

Find the opposite side with the cosine rule.

All lengths must use the same unit. Area uses squared units and volume uses cubed units. Finite real inputs; output uses up to 12 significant digits. Floating-point results may be rounded. Included angle is strictly between 0 and 180 degrees. This solves SAS only, without ambiguous SSA cases. Finite real inputs; output uses up to 12 significant digits. Floating-point results may be rounded.

Concept diagram for Triangle Side Calculator, showing first adjacent side input and the supported output.
Concept diagram; the three operation images are actual browser captures.

How to use Triangle Side Calculator

Follow the labelled inputs.

Enter first adjacent side

Replace the example with first adjacent side. The field labels specify the expected format and units.

Calculate
Input and settings
Triangle Side Calculator: input and settings in the implemented browser tool
Actual local browser view. Open the image to read it at full size.

Check the remaining inputs

Set second adjacent side, included angle (degrees). All lengths must use the same unit.

Calculate
Tool result
Triangle Side Calculator: tool result in the implemented browser tool
Actual local browser view. Open the image to read it at full size.

Run, review and save

Select Calculate. Review the calculated result, then copy it or download the result text.

Calculate
Review the details
Triangle Side Calculator: review the details in the implemented browser tool
Actual local browser view. Open the image to read it at full size.

Examples and uses for Triangle Side Calculator

Check the supplied example

The starting example produces 5. Find the opposite side with the cosine rule.

Calculate
Abstract input values and a mathematical worksheet.
Start with the values. Concept illustration.

Use your own inputs

Read the labels for first adjacent side and second adjacent side, included angle (degrees). All lengths must use the same unit.

Calculate
Two calculation examples shown for comparison.
Compare a second example. Concept illustration.

Record a reviewed result

Copy the calculated result into your notes. Keep the formula and assumptions with it if someone else needs to reproduce the calculation.

Calculate
A calculation and supporting explanation represented conceptually.
Explain the calculation. Concept illustration.

How to read the result

Read the units and assumptions with the output.

Find the opposite side with the cosine rule.

All lengths must use the same unit. Area uses squared units and volume uses cubed units. Finite real inputs; output uses up to 12 significant digits. Floating-point results may be rounded. Included angle is strictly between 0 and 180 degrees. This solves SAS only, without ambiguous SSA cases. Finite real inputs; output uses up to 12 significant digits. Floating-point results may be rounded.

CalculateCalculate
A mathematical result connected to the values used to calculate it.
Read the result with its inputs. Concept illustration.

Supported input and limits

Check the stated scope before you run it.

All lengths must use the same unit. Area uses squared units and volume uses cubed units. Finite real inputs; output uses up to 12 significant digits. Floating-point results may be rounded. Included angle is strictly between 0 and 180 degrees. This solves SAS only, without ambiguous SSA cases. Finite real inputs; output uses up to 12 significant digits. Floating-point results may be rounded.

The input stays in this browser. Copy result and Download save the same displayed text.

CalculateCalculate
Values and units reviewed before relying on a mathematical result.
Check values and units. Concept illustration.

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Triangle Side Calculator: common questions

Answers about using Triangle Side Calculator and understanding its results.

What assumptions and input limits apply?

All lengths must use the same unit. Area uses squared units and volume uses cubed units. Finite real inputs; output uses up to 12 significant digits. Floating-point results may be rounded. Included angle is strictly between 0 and 180 degrees. This solves SAS only, without ambiguous SSA cases. Finite real inputs; output uses up to 12 significant digits. Floating-point results may be rounded.

How can I save the output?

Use Copy result to copy the displayed text, or Download to save it as a text file. The tool runs in your browser and does not require an account.

Calculate with your input

Check the calculated result, then copy or download it.

Calculate