PT is the tangent PAB is a secant if AB = 5cm, PT = 6cm, find the length of PA?

Asked by YOGIRAJ Karambelkar | 27th Feb, 2013, 05:32: PM

Expert Answer:

Let the length of PA = x cm
 
By using the theorem which says that in a circle, if PAB is the secant and PT is the tangent, then PT2 = PA. PB
 
Hence, here also,  
PT2 = PA. PB
62 = x. (x+5)
x2 +5x -36 = 0
(x+9) (x-4) = 0
x = -9 or x = 4
Since, x can't be negative, hence, x = 4
i.e. length of PA = 4 cm

Answered by  | 27th Feb, 2013, 08:19: PM

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