Circle Theorems Calculator
Angles from circle theorems: angle at the centre, in a semicircle, in the same segment and tangent-chord.
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Angles from circle theorems: angle at the centre, in a semicircle, in the same segment and tangent-chord.
Circle Theorems Estimator
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How It Works
Key concepts behind this calculator
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Circle Quick Guide
Typical values for reference.
| Theorem | Rule | Example | Result |
|---|---|---|---|
| Centre angle | 2 x circumference angle | 35 deg | 70 deg |
| Semicircle | Always 90 deg | Any | 90 deg |
| Cyclic quadrilateral | Opposite angles sum to 180 | 110 deg | 70 deg |
| Tangent-chord | Equals alternate segment angle | 40 deg | 40 deg |
| Rule of Thumb | Check inputs | Use as a guide | Round sensibly |
Circle Theorems Calculator FAQ
Answers to common questions about this calculator.
The angle at the centre is twice the angle at the circumference.
Always 90 degrees.
Centre angle = 2 x angle at the circumference.
It is an estimate based on the inputs you enter. Check real quotes, labels or official guidance for important decisions.