Q) Two tangents TP and TQ are drawn to a circle with centre 0 from an external point T. Prove that PTQ = 2OPQ.

Circles 1

Ans:

TP = TQ

⇒ ∠TPQ = ∠TQP

Let ∠PTQ be θ

⇒ ∠TPQ = ∠TQP = \frac{180 - \theta}{2}

= 90° – (\frac{\theta}{2})  

Now, ∠OPT  = 90°

⇒ ∠OPQ  = 90°  – [90° – (\frac{\theta}{2})] = (\frac{\theta}{2} )

\therefore ∠PTQ = 2 ∠OPQ ….  Hence Proved

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