Edexcel IGCSE Maths 復習筆記 4.6.3 Circle Theorems - Cyclic Quadrilaterals
Edexcel IGCSE Maths 復習筆記 4.6.3 Circle Theorems - Cyclic Quadrilaterals
More advanced circle theorems
1. Opposite angles in a cyclic quadrilateral add up to 180°
- Double-check is that all 4 vertices of the quadrilateral are on the circumference
- The diagram below shows a common scenario that is?NOT?a cyclic quadrilateral:
2. The perpendicular bisector of a chord is a radius
- This is also easier to see than remember from its description
- Problems here involve the radii being joined to the end of the chords and so creating two congruent triangles
Exam Tip
Remember to add anything you can to a diagram you have been given – write in any angles and lengths you can work out, even if they don’t seem relevant to the actual question.
Worked Example
Worked Example
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