If an equilateral triangle is inscribed in the circle x2 + y2 = a

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 Multiple Choice QuestionsMultiple Choice Questions

451.

If the tangent at the point 2secθ, 3tanθ of the hyperbola x24 - y29 = 1 is parallel to 3x - y + 4 = 0, then the value of θ is

  • π4

  • π3

  • π6

  • π2


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452.

If an equilateral triangle is inscribed in the circle x2 + y2 = a2, the lenth of its each side is

  • 2a

  • 3a

  • 32a

  • 13a


B.

3a

Given equation of the circle is         x2 + y2 = a2where, radius = a

let ABC be the inscribed equnateral triangle and length of its each sides be l,

Area of ABC = 34l2Also, OD = a2 - l24     from ODB Area of OBC = 12 × l × a2 - l24Now, area of ABC = 3 × Area of OBC 34l2 = 3 × l2a2 - l24   3l = 34a2 - l2     3l2 = 94a2 - l2       l2 = 12a2 - 3l2     4l2 = 12a2       l2 = 3a2        l = 3a


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453.

If the vertex is (3,0) and the extremities of the latusrectum are (4, 3) and (4, - 3), then the equation of the parabola is

  • y2 = 4(x - 3)

  • x2 = 4(y - 3)

  • y2 = - 4(x + 3)

  • x2 = - 4(y + 3)


454.

If the line x + 2by + 7 = 0 is a diameter of the circle x2 + y2 - 6x + zy = 0, then b is equal to

  • - 5

  • - 3

  • 2

  • 5


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455.

If the line y = 2x+ c is tangent to the parabola y2 = 4x, then c is equal to

  • - 12

  • 12

  • 13

  • 14


456.

The length of the latus rectum of the ellipse 9x2 + 4y2 = 1 is

  • 32

  • 49

  • 83

  • 89


457.

The number of circles that touch all the straight lines x + y = 4,x - y = - 2 and y = 2 is

  • 1

  • 2

  • 3

  • 4


458.

The equation of the normal to the circle x2 + y2 + 6x + 4y - 3 = 0 at (1, - 2) is

  • y + 1 = 0

  • y + 2 = 0

  • y + 3 = 0

  • y - 2 = 0


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459.

The limiting points of the co-axial system containing the two circles x2 + y2 + 2x - 2y + 2 = 0 and 25(x2 + y) - 10x - 80y + 65 = 0 are

  • (1, - 1), (- 3, - 40)

  • 1, - 1, - 15, 85

  • - 1, 1, 15, 85

  • - 15, - 85


460.

The radical axis of circles x2 + y2 + 5x + 4y - 5 = 0 and x2 + y2 - 3x + 5y - 6 = 0 is

  • 8y - x + 1 = 0

  • 8x - y+ 1 = 0

  • 8x - 8y + 1 = 0

  • y - 8x + 1 = 0


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