NCERT Exemplar Solutions
Class 10 - Mathematics - CHAPTER 9: Circles - Exercise 9.2
Question 1

Question. 1

If a chord \(AB\) subtends an angle of \(60^\circ\) at the centre of a circle, then the angle between the tangents at \(A\) and \(B\) is also \(60^\circ\). State True/False and justify.

Answer:

False.

Detailed Answer with Explanation:

Step 1: In a circle, when we join the radii \(OA\) and \(OB\) (where \(O\) is the centre), the angle at the centre is given as \(\angle AOB = 60^\circ\).

Step 2: At point \(A\), the tangent is always perpendicular to the radius \(OA\). Similarly, at point \(B\), the tangent is perpendicular to the radius \(OB\).

Step 3: Therefore, the angle formed between the two tangents at points \(A\) and \(B\), say \(\theta\), is related to the angle at the centre by the rule:

\(\theta + \angle AOB = 180^\circ\)

Step 4: Substitute the given value \(\angle AOB = 60^\circ\):

\(\theta + 60^\circ = 180^\circ\)

Step 5: Solve for \(\theta\):

\(\theta = 180^\circ - 60^\circ = 120^\circ\)

Final Answer: The angle between the tangents is \(120^\circ\), not \(60^\circ\). Hence, the given statement is False.

NCERT Exemplar Solutions Class 10 – Mathematics – CHAPTER 9: Circles – Exercise 9.2 | Detailed Answers