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If PA and PB are tangents from an outside point P such that PA = 6 cm and angle APB = 60° .find the length of the CHORD AB.

Given:-

PA and PB are tangents of a circle, PA = 10 cm and ∠APB = 60°

To find:-

Length Of Chord AB.

Step By Step Explanation:-

Let O be the center of the given circle and C be the point of intersection of OP and AB.

In ΔPAC and ΔPBC,

》PA = PB (Tangents from an external point are equal)

》∠APC = ∠BPC (Tangents from an external point are equally inclined to the segment joining center to that point)

》PC = PC (COMMON)

Thus, ΔPAC is congruent to ΔPBC (By SAS congruency rule) ..........(1)

∴ AC = BC

Also ∠APB = ∠APC + ∠BPC

∠APC= ∠APB.

[Since,∠APC = ∠BPC]

×60° = 30°

∠ACP + ∠BCP = 180°. {∠ACP =∠BCP}

∠ACP = × 180°

Now, In right triangle ACP,

sin30° =

=

AC = × 10 = 5

∴ AB = AC + BC = AC + AC (AC = BC)

⇒ AB = 5CM + 5cm

⇒ AB = 10CM.