The locus ofthe point of intersection of the lines xcos&alph

Subject

Mathematics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

11.

If the algebraic sum of the perpendicular distances from the points (2, 0), (0, 2) and (1, 1) on a variable line is zero, then the line will pass through the fixed point

  • (1, 2)

  • (1, 1)

  • (0, 0)

  • (2, 1)


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12.

The locus ofthe point of intersection of the lines xcosα + ysinα = p and xsinα - ycosα = q (α is a variable) will be

  • a circle

  • a staright line

  • a parabola

  • an ellipse


A.

a circle

Let (x1 , y1) be the point of intersection of the given lines.x1cosα + y1sinα = px1sinα - y1cosα = qOn squaring and adding, we getx12cos2α + sin2α + y1cos2α + sin2α = p2 + q2 x12 + y12 = p2 + q2Hence, locus of a point is         x2 + y2 = p2 + q2which represent the equation of circle.


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13.

The locus of the mid points of the chords of a circle which subtend a right angle at its centre (equation ofthe circle is x2 + y2 = a2)will be

  • x2 + y2 = 3a2

  • x2 + y2a23

  • 2(x2 + y2) = a2

  • 4(x2 + y2) = a2


14.

If the line 3x - 2y + p = 0 is normal to the circle x2 + y2 = 2x - 4y - 1, then p will be

  • - 5

  • 7

  • - 7

  • 5


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15.

If the two circles x2 + y2 = r2 and x2 + y2 - 10x + 16 = 0 intersect at two real points, then

  • 1 < r < 7

  • 3 < r < 10

  • 2 < r < 9

  • 2 < r < 8


16.

The equation of the common tangent to the parabolas y2 = 2x and x2 = 16y will be

  • x + y + 2 = 0

  • x - 3y + 1 = 0

  • x + 2y - 2 = 0

  • x + 2y + 2 = 0


17.

The equation of the tangent to the parabola y2 = 8x, which is parallel to the line 2x - y + 7 = 0, will be

  • y = x + 1

  • y = 2x + 1

  • y = 3x + 1

  • y = 4x + 1


18.

The distance of a point on ellipse x26 + y22 = 1 from its centre is 2. The eccentric angle of the point will be

  • π4 or π3

  • π3 or 3π5

  • π4 or 3π4

  • None of these


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19.

The distance between the foci of a hyperbola is 16 and its eccentncity is 2. Its equation will be

  • x2 - y2 = 1

  • x2 - y2 = 20

  • x2 - y2 = 4

  • x2 - y2 = 32


20.

The point on x2 = 2y, which is closest to the point (0, 5), will be

  • 22, 0

  • (0, 0)

  • (2, 2)

  • None of these


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