Circles

(a) If a, b, c are the sides of a right triangle where c is the hypotenuse, prove that the radius r of the circle which touches the sides of the triangle is given by r = /frac (a + b – c) – (2) (b) In the given figure, PB is a tangent to a circle with center O at B. AB is a chord of length 24 cm at a distance of 5 cm from the center. If the length of the tangent is 20 cm, find the length of OP.

Solution: (a) Let the circle touch the sides BC, CA and AB of the right triangle ABC at points D, E and F respectively, where BC = a, CA = b and AB = c (as showing in the given figure). As the...

read more

(a) In the figure (i) given below, O is the center of the circle. If ∠AOC = 150°, find (i) ∠ABC (ii) ∠ADC (b) In the figure (i) given below, AC is a diameter of the given circle and ∠BCD = 75°. Calculate the size of (i) ∠ABC (ii) ∠EAF.

Solution: (a) Given, ∠AOC = 150° and AD = CD We know that an angle subtends by an arc of a circle at the center is twice the angle subtended by the same arc at any point on the remaining part of the...

read more

(a) In the figure (i) given below, M, A, B, N are points on a circle having centre O. AN and MB cut at Y. If ∠NYB = 50° and ∠YNB = 20°, find ∠MAN and the reflex angle MON. (b) In the figure (ii) given below, O is the centre of the circle. If ∠AOB = 140° and ∠OAC = 50°, find (i) ∠ACB (ii) ∠OBC (iii) ∠OAB (iv) ∠CBA

Solution (a) ∠NYB = 50°, ∠YNB = 20°. In ∆YNB, ∠NYB + ∠YNB + ∠YBN = 180o 50o + 20o + ∠YBN = 180o ∠YBN + 70o = 180o ∠YBN = 180o – 70o = 110o But ∠MAN = ∠YBN (Angles in the same segment) ∠MAN = 110o...

read more

Two congruent circles have their centers at O and P respectively . Line segment OP has the midpoint M. A straight line is drawn through M cutting the two circles at the points A, B, C and D. We need to Prove that the chords of the circle AB and CD are equal.

From the question it is given that, O and P are the centers of the congruent circles. Line segment OP has the midpoint M To Prove:, Chord AB and CD are equal. Then, draw $OQ\bot AB$ and $PR\bot CD$....

read more

Two circles of radii $5cm$ and $3cm$ with centers O and P touch each other internally. If the perpendicular bisector of the line segment OP meets the circumference of the larger circle at A and B, find the length of AB (chord of the larger circle).

From the question it is given that, Radius of bigger circle $=5cm$ Radius of smaller circle $=3cm$ Then, $OA=AH=5cm$… [both are radius of bigger circle] $PH=3cm$ … [radius of smaller circle]...

read more

What will be the length of the chord of a circle in each of the following when:(i) The circle has the radius $13cm$ and the distance of the chord from the center is $12cm$(ii) The circle of the radius is $1.7cm$ and the distance of the chord from the center is $1.5cm$.

Given:  Radius $=13cm$ Distance of chord from the center is $12cm$ Therefore, $PR=RQ$We know that perpendicular from center to a chord bisects the chord of the circle. Consider the...

read more