Radius perpendicular to tangent
The radius drawn to the point of contact of a tangent is perpendicular to the tangent.
Practice This ConceptMain explanation
Teacher explanation
This is one of the most important tangent properties in Class 10. If a tangent touches the circle at point P, then the radius from the centre to P makes a 90 degree angle with the tangent. This result is often used in proofs and angle questions.
Example
If OA is a radius and line l is tangent at A, then OA is perpendicular to l.
Simple analogy
Radius and tangent make a right angle at the touch point.
Common confusion
Students often write that the radius is parallel to the tangent, which is opposite to the actual theorem.
Exam tip
Whenever you see a tangent and radius meeting at the contact point, mark a right angle immediately.
Answer writing and exam use
1-mark use
Write the exact meaning of radius perpendicular to tangent in one clean line.
2-mark use
Define radius perpendicular to tangent and add one example or condition.
3-mark use
Explain radius perpendicular to tangent, show the method or example, and mention the common mistake.
Practice this concept with focused MCQs
Open the concept quiz intro first, review the test details, and then start a focused MCQ set from this concept only. Instant score and answer review are live now.
Help improve this page
Found something confusing, incorrect, or missing?