GCSE Maths (Edexcel)
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Tangents Meeting
- Two tangents drawn from a point to a circle are equal in length
- The theorem can be proven using congruent triangles and the relation between a radius and a tangent
- Draw a line from the center of the circle to where the tangents meet to create two triangles
- Deduce that the angles where the radii meet the tangents are 90 degrees
- State the relation between the two radii (OA = OC)
- Show that the two triangles are congruent using the RHS condition
- Deduce that the other side lengths are equal (AB = CB)
- Prove the theorem that the two tangents have the same length since they originate from the same point
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