1.

In the given figure, PT is a tangent and PAB is a secant. If PT=6 cm and AB=5 cm, then find the length of PA.

Answer» Let `PA = x` cm
As `PT` is the tangent and `PAB` is secant,
`:. PT^2 = PA**PB`
`=>PT^2 = PA**(5+PA)`
`=>6^2 = x(5+x)`
`=>x^2+5x-36 = 0`
`=>x^2+9x-4x-36 = 0`
`=>(x+9)(x-4) = 0`
`=. x = -9 and x =4`
But, `x` can not be negative, so `x = 4`.
`:. PA = x = 4cm`


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