Plane Geometry
- Number of circles that can be drawn through three non-collinear points is :
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One and only one circle can pass through three non-collinear points.
Correct Option: A
On the basis of given question ,
We can say that One and only one circle can pass through three non-collinear points.
- The length of a chord which is at a distance of 12 cm from the centre of a circle of radius 13 cm is
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As per the given in question , we draw a figure of a circle with centre O,
OC ⊥ AB
∴ AC = CB
OA = 13 cm. , OC = 12 cm.
In ∆ OAC, AC = √OA² - OC²
AC = √13² - 12²Correct Option: A
As per the given in question , we draw a figure of a circle with centre O,
OC ⊥ AB
∴ AC = CB
OA = 13 cm. , OC = 12 cm.
In ∆ OAC, AC = √OA² - OC²
AC = √13² - 12²
AC = √(13 + 12)(13 - 12)
AC = √25 = 5 cm.
∴ AB = 2 AC = 10 cm.
- Points P, Q and R are on a circle such that∠PQR = 40° and ∠QRP = 60°. Then the subtended angle by arc QR at the centre is :
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According to question , we draw a figure of a circle with centre O ,
In ∆ PQR,
∠PQR = 40° ; ∠QRP = 60°
∴ ∠QPR = 180° – 60° – 40° = 80°Correct Option: D
According to question , we draw a figure of a circle with centre O ,
In ∆ PQR,
∠PQR = 40° ; ∠QRP = 60°
∴ ∠QPR = 180° – 60° – 40° = 80°
∴ Angle subtended at the circumference by arc QR = 80°
∴ Angle subtended at the centre by arc QR = ∠QOR = 2∠QPR = 2 × 80° = 160°
- Two circles touch each other externally. The distance between their centres is 7 cm. If the radius of one circle is 4 cm, then the radius of the other circle will be
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On the basis of question we draw a figure of two circles touch each other externally ,
Correct Option: A
On the basis of question we draw a figure of two circles touch each other externally ,
We know that , Distance between two circles = OO' = r1 + r2 = 7 cm.
r1 = 4 cm.
∴ r2 = (7 – 4) cm. = 3 cm.
- The length of the radius of a circle with centre O is 5 cm and the length of the chord AB is 8 cm. The distance of the chord AB from the point O is
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On the basis of question we draw a figure of a circle with centre O and radius is 5 cm ,
Here , OA = radius = 5 cm.
OC ⊥ AB∴ AC = CB = 8 = 4 cm. 2
In right angle ∆ OAC,
Correct Option: B
On the basis of question we draw a figure of a circle with centre O and radius is 5 cm ,
Here , OA = radius = 5 cm.
OC ⊥ AB∴ AC = CB = 8 = 4 cm. 2
In right angle ∆ OAC,
OC = √OA² - AC² = √5² - 4²
OC = √25 - 16 = √9 = 3 cm.