Plane Geometry
- In a triangle ABC, AB + BC = 12 cm, BC + CA = 14 cm and CA + AB = 18 cm. Find the radius of the circle (in cm) which has the same perimeter as the triangle.
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Given that , AB + BC = 12
BC + CA = 14
CA + AB = 18
On adding , we get
∴ 2(AB + BC + CA) = 12 + 14 + 18 = 44
⇒ AB + BC + CA = 22
∴ 2πr = 22⇒ 2 × 22 × r = 22 7
Correct Option: B
Given that , AB + BC = 12
BC + CA = 14
CA + AB = 18
On adding , we get
∴ 2(AB + BC + CA) = 12 + 14 + 18 = 44
⇒ AB + BC + CA = 22
∴ 2πr = 22⇒ 2 × 22 × r = 22 7 ⇒ r = 7 cm 2
- If I be the incentre of ∆ ABC and ∠B = 70° and ∠C = 50°, then the magnitude of ∠BIC is
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Firstly , We draw a figure of triangle ABC whose I is incentre ,
Here , ∠B = 70° and ∠C = 50°∠IBC = 70° = 35° ; 2 ∠ICB = 50° = 25° ; 2
Correct Option: C
Firstly , We draw a figure of triangle ABC whose I is incentre ,
Here , ∠B = 70° and ∠C = 50°∠IBC = 70° = 35° ; 2 ∠ICB = 50° = 25° ; 2
We know that , ∠BIC + ∠ICB + ∠IBC = 180°
∴ ∠BIC = 180° – 35° – 25°
∠BIC = 180° – 60° = 120°
- For a triangle ABC, D, E, F are the mid-points of its sides. If ∆ABC = 24 sq. units then ∆DEF is
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On the basis of given in question , we draw a figure triangle ABC ,
Here , ∆ABC = 24 sq. units
From figure , we have∆DEF = 1 ∆ ABC 4
Correct Option: B
On the basis of given in question , we draw a figure triangle ABC ,
Here , ∆ABC = 24 sq. units
From figure , we have∆DEF = 1 ∆ ABC 4 ∆DEF = 1 × 24 = 6 Sq. unit 4
- Angle between sss ∠B is
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As per the given in question , we draw a figure of triangle ABC
∠BPC = 120°
∴ ∠PBC + ∠PCB = 180°– 120°= 60°Correct Option: D
As per the given in question , we draw a figure of triangle ABC
∠BPC = 120°
∴ ∠PBC + ∠PCB = 180°– 120°= 60°
∴ ∠ABC + ∠ACB = 2 × 60° = 120°
∴ ∠A = 180 – 120 = 60°
- In a ∆ABC, ∠A + ∠B = 70° and ∠B + ∠C = 130°, value of ∠A is
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In ∆ ABC,
As we know that , ∠A + ∠B + ∠C = 180°
Given , ∠A + ∠B = 70° and ∠B + ∠C = 130°Correct Option: B
In ∆ ABC,
As we know that , ∠A + ∠B + ∠C = 180°
Given , ∠A + ∠B = 70° and ∠B + ∠C = 130°
∴ ∠A = (∠A + ∠B + ∠C) – (∠B + ∠C)
∠A = 180– 130°= 50°