Plane Geometry


  1. ∆ ABC is inscribed in a circle so that BC is diameter. The tangent at a point C intersects BA when produced at a point D. If ∠ABC = 36° then the value of ∠ADC is









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    According to question , we draw a figure of ∆ ABC in which inscribed in a circle

    The angle at the circumference of a semi–circle is a right angle.
    ∴ ∠BAC = 90°
    ∠ABC = 36°
    ∴ ∠ACB = 90° – 36° = 54°
    ∠BCD = 90°

    Correct Option: D

    According to question , we draw a figure of ∆ ABC in which inscribed in a circle

    The angle at the circumference of a semi–circle is a right angle.
    ∴ ∠BAC = 90°
    ∠ABC = 36°
    ∴ ∠ACB = 90° – 36° = 54°
    ∠BCD = 90°
    ∴ ∠ACD = 90° – 54° = 36°
    ∠DAC = 90°
    ∴ ∠ADC = 90° – 36° = 54°


  1. There are two equal circles of radius 3 cm each and distance between their centres is 10 cm. The length of one of their transverse common tangents is









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    As per the given in question , we draw a figure of two equal circles
    Transverse common tangent = √d² - (r1 + r2
    Transverse common tangent = √10² - (3 + 3)²
    [ r1 = r2 = 3 cm.]
    Transverse common tangent = √100 - 36

    Correct Option: D

    As per the given in question , we draw a figure of two equal circles
    Transverse common tangent = √d² - (r1 + r2
    Transverse common tangent = √10² - (3 + 3)²
    [ r1 = r2 = 3 cm.]
    Transverse common tangent = √100 - 36
    Transverse common tangent = √64 = 8 cm.



  1. The maximum number of common tangents that can be drawn to two disjoint circles is









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    According to question , we draw a figure

    Correct Option: C

    According to question , we draw a figure

    Maximum No. of Common tangents = 4


  1. How many common tangents can be drawn on two circles touching each other externally?









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    As per the given in question , we draw a figure two circles touching each other externally

    Correct Option: D

    As per the given in question , we draw a figure two circles touching each other externally

    No. of common tangents = 3



  1. A chord of a circle is equal to its radius. A tangent is drawn to the circle at an extremity of the chord. The angle between the tangent and the chord is









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    According to question , we draw a figure of a circle with centre O

    OB = OC = radii
    ∴ In ∆ OBC,
    OB = BC = CO

    Correct Option: A

    According to question , we draw a figure of a circle with centre O

    OB = OC = radii
    ∴ In ∆ OBC,
    OB = BC = CO
    ∴ ∠OCB = ∠OBC = ∠BOC = 60°
    OC ⊥ DE
    ∴ ∠BCD = 90° – 60° = 30°