In Figure, if PQR is the tangent to a circle at Q whose centre is O, AB is a chord parallel to PR and BQR = 70°,then AQB is equal to
(A) 20° (B) 40° (C) 35° (D) 45°
Answer(B)
Solution
Given :,
Since DQ perpendicular to PR
Since DQ bisect
Hence ,
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If two tangents inclined at an angle 60° are drawn to a circle of radius 3 cm,then length of each tangent is equal to
(A) (B) 6 cm (C) 3 cm (D)
Answer (D)
Solution
According to question
Given OQ = OR = 3 cm (Radius)
Draw line OP which bisect . That is
In
Here PQ = PR
Hence , PQ = PR=
In Figure, if PA and PB are tangents to the circle with centre O such that APB = 50°, then OAB is equal to
(A) 25° (B) 30° (C) 40° (D) 50°
Answer (A) 25°
Solution
Given : APB = 50°
We know that length of tangents drawn from an external point is equal
Hence, PA = PB
Since, PA = PB
Let PAB = PBA = x0
In PAB
p+A+B = ( Sum of interior angles of a tangent is )
PAB = PBA =
PAO = ( tangent is perpendicular to radius)
PAO = PAB +OAB
In Figure, if O is the centre of a circle, PQ is a chord and the tangent PR at P makes an angle of 50° with PQ, then ∠POQ is equal to
(A) 100° (B) 80° (C) 90° (D) 75°
Answer(A)
Solution
Given :
We know that tangent is perpendicular to radius.
Hence
OPR =
OPR = OPQ + QPR
= OPQ +
OPQ =
OPQ = OQD
Hence , OPQ =
We know that the sum of interior angles of a triangle is
In
O+Q +P =
O +40+40 = 180
o =
Hence OPQ =
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In Figure, AT is a tangent to the circle with centre O such that OT = 4 cm and ∠OTA = 30°. Then AT is equal to
(A) 4 cm (B) 2 cm (C) (D)
Answer(C)
Solution
Given ∠OTA = 30° , OT = 4cm
Join OA, since AT is tangent.
Hence it is perpendicular to OA
In OAT
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At one end A of a diameter AB of a circle of radius 5 cm, tangent XAY is drawn to the circle. The length of the chord CD parallel to XY and at a distance 8 cm from A is
(A) 4 cm (B) 5 cm (C) 6 cm (D) 8 cm
Answer (D) 8 cm
Solution
According to questions
Given AO = OB = 5 cm
Distance between XY and CD = 8 cm
Since D is the center of the circle and CD is chord. If we join OD it become the radius of circle that is OD = 5cm
AZ = 8 cm (given)
AZ = AO + OZ
8 = 5 + OZ
OZ = 3cm
In ODZ, use Pythagoras theorem
Length of chord CD = 8 cm
From a point P which is at a distance of 13 cm from the centre O of a circle of radius 5 cm, the pair of tangents PQ and PR to the circle are drawn. Then the area of the quadrilateral PQOR is
(A) 60 cm2 (B) 65 cm2 (C) 30 cm2 (D) 32.5 cm2
Answer (A) 60 cm2
Solution
According to question
Given OP = 13 cm
OQ = OR = radius = 5 cm
In POQ, ( PQ is tangent)
Using Pythagoras theorem in POQ
( because H2 = B2 + P2)
Area of POQ = × perpendicular × base
Area of quadrilateral = 2 × area of POQ
= 2 × 30 = 60 cm2
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In Figure, AB is a chord of the circle and AOC is its diameter such that ACB = 50°. If AT is the tangent to the circle at the point A, then BAT is equal to
(A) 65° (B) 60° (C) 50° (D) 40°
Answer (C)
Solution
Given ACB = 50°.
We know that the angle subtended by a diameter is right.
Hence B = 90°
We know that sum of interior angle of a triangle is 180°.
In ABC
That is
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In Figure, if ∠AOB = 125°, then ∠COD is equal to
(A) 62.5° (B) 45° (C) 35° (D) 55°
Answer (D)
Solution
Given : ∠AOB = 125°
Let ∠COD = x°
As we know that the sum of opposite sides angles of a quadrilateral circumscribing a circle is equal to 180°.
Hence
∠AOB + ∠COD = 180°
125° + ∠COD = 180°
x° = 180° – 125° ( ∠COD = x°)
x° = 55°
Hence, ∠COD = 55°
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If radii of two concentric circles are 4 cm and 5 cm, then the length of each chord of one circle which is tangent to the other circle is
(A) 3 cm (B) 6 cm (C) 9 cm (D) 1 cm
Answer (B) 6 cm
Solution
According to question
Here A is the center and AB = 4 cm radius of small circle and AD = 5 cm radius of large circle.
We have to find the length of CD
ABD is a right angle triangle.
Hence use Pythagoras theorem in ABD
Hence length of chord is 6 cm.
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