## Book: RS Aggarwal - Mathematics

### Chapter: 12. Circles

#### Subject: Maths - Class 10th

##### Q. No. 21 of Multiple Choice Questions (MCQ)

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21
##### If two tangents inclined at an angle of 60° are drawn to a circle of radius 3 cm then the length of each tangent is

Let us consider a circle with center O and AP and BP are two tangents such that angle of inclination i.e. APB = 60°

Joined OA, OB and OP.

To Find : Length of tangents

Now,

PA = PB [Tangents drawn from an external point are equal] [1]

In AOP and BOP

PA = PB [By 1]

OP = OP [Common]

OA = OB [radii of same circle]

AOP ≅△BOP

[By Side - Side - Side Criterion]

OPA = OPB

[Corresponding parts of congruent triangles are congruent]

Now,

APB = 60° [Given]

OPA + OPB = 60°

OPA + OPA = 60°

2 OPA = 60°

OPA = 30°

In AOP

OA PA

[Tangents drawn at a point on circle is perpendicular to the radius through point of contact

AOP is a right - angled triangle.

So, we have

PA = 3√3 cm

From [1]

PA = PB = 4 cm

i.e. length of each tangent is 3√3 cm

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