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Triangle Calculator
Solve any triangle from three sides or two sides and the angle between them: angles, area, perimeter and type.
Circle Equation Calculator
Write the equation of a circle from its center and radius, or find the center and radius from the general form.
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How to use this calculator
Enter your values after choosing the type of calculation in the tabs. The result updates as you type; press Calculate to confirm and jump to the result on mobile. Use Share to send the calculator with your result.
Circle equations
Standard: (x − h)² + (y − k)² = r²
General: x² + y² + Dx + Ey + F = 0
h = −D/2, k = −E/2, r = √(h² + k² − F)
Example: center (2, −3), radius 5 → (x − 2)² + (y + 3)² = 25, which expands to x² + y² − 4x + 6y − 12 = 0.
Frequently asked questions
How do I find the radius from the general form?
Complete the square: r = √((D/2)² + (E/2)² − F).
About this tool
- Written by
- [Author: to be assigned]
- Reviewed by
- Formula tests passed · human review pending
- Last updated
- 31 Oct 2026
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