Brainlag PlusThe right angle between a tangent and a radius, two equal tangents from a point, and the alternate segment theorem.
Tangent and radius
A tangent touches the circle at one point, T.
The radius OT meets it at exactly 90°. So triangle OTP, for any point P on the tangent, is right-angled at T: use angle facts or Pythagoras, with OP as the hypotenuse.
Not drawn accurately
- OP² = 5² + 12² = 25 + 144 = 169
- OP = 13 cm
The rest of this lesson and its 7 practice questions are in Plus.
Screen 1 of 4, free to read.
- 7 exam-style questions, marked as you go, each with a worked solution
- The Circle theorems simulation beside every question
- Anything you get wrong is saved to your flashcards