In the figure given, PA= 4 cm, AB= 9 cm, then value of PT is

We know that for a secant PAB to a circle intersecting the circle to A and B and PT is a tangent, then PA × PB = PT² 

Here is the link for the proof of the same

https://www.meritnation.com/ask-answer/question/dear-meritnation-experts-plz-answer-my-question-if-pab-i/circles/1726596

Thus, PA = 4 cm, PB = PA + AB = 4 cm + 9 cm = 13cm

Hence, PT² = 4 cm × 13cm = 52 cm²

⇒ PT = √52 cm = 2√13 cm