Online tangent-secant theorem calculator. Enter the near and far segments of a secant from an outside point to find the tangent length (tangent² = product)—great for circle power.
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PT² = PA·PB
Near distance
Far distance
📖 Tutorial | Tangent-Secant
1. Definition
For a tangent PT and secant PAB (near A, far B), PT²=PA·PB.
2. Formula & Notation
PT
Tangent length
PA, PB
Near, far
3. Properties & Laws
PT²=PA·PB;
PT=√(near×far);
Unified by power of a point;
Far>near.
4. Steps
Enter near a, far b;
Click "Find Tangent";
Or click "Load Example".
5. Worked Examples
Example: near 4, far 9. Solution: PT = √36 = 6.
6. Common Pitfalls
Tangent²=near×far; Far exceeds near; Take the square root.