Subject

Mathematics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

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11.

If sinAsinC = sinA - BsinB - C, then a2, b2, c2 are in

  • AP

  • GP

  • HP

  • None of these


A.

AP

sinAsinC = sinA - BsinB - CsinAsinC = sinA . cosB - cosA . sinBsinB . cosC - cosB . sinCaKcK = aKcosB - bKcosAbKcosC - cKcosB         sinAa = sinBb = sinCc = Kac = acosB - bcosAbcosC - ccosB          cosA = b2 + c2 - a22bccosB = a2 + c2 - b22accosC = a2 + b2 - c22abac = a2 + c2 - b22c - b2 + c2 - a22ca2 + b2 - c22a - a2 + c2 - b22a

    = aca2 + c2 - b2 - c2 - b2 + a2a2 + b2 - c2 - a2 - c2 + b21 = 2a2 - 2b22b2 - 2c2 1 = a2 - b2b2 - c2 b2 - c2 = a2 - b2       2b2 = a2 + b2Hence, a2, b2, c2 are in AP.


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12.

If A = 60°, a = 5, b = 43 in ABC, then B is equal to

  • 30°

  • 60°

  • 90°

  • None of these


13.

If a + b + c = 0, the straight line 2ax + 3by + 4c = 0 passes through the fixed point

  • 2, 43

  • (2, 2)

  • 43, 43

  • No such fixed point


14.

The orthocentre of the triangle formed by tie lines xy = 0 and x + y = 1 is

  • 12, 12

  • 13, 13

  • (0, 0)

  • 14, 14


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15.

Equation of the circle which passes through the origin and cuts intercepts of lengths a and b on axes is

  • x2 + y2 + ax + by = 0

  • x2 + y2 + ax - by = 0

  • x2 + y2 + bx + ay = 0

  • None of the above


16.

If focus ofa parabolais at (3, 3) and its directrix is 3x - 4y = 2, then its latusrectum is

  • 2

  • 3

  • 4

  • 5


17.

If the straight line y = 4x + c is a tangent to the ellipse x28 + y24 = 1, then c will be equal to

  • ± 4

  • ± 6

  • ± 1

  • ± 132


18.

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

  • x2 - y2 = 32

  • y2 - x2 = 32

  • x2 - y2 = 16

  • y2 - x2 = 16


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19.

The locus of the point, which moves such that its distance from (1, - 2, 2) is unity, will be

  • x2 + y2 + z2 - 2x + 4y - 4z + 8 = 0

  • x2 + y2 + z2 - 2x - 4y - 4z + 8 = 0

  • x2 + y2 + z2 + 2x + 4y - 4z + 8 = 0

  • x2 + y2 + z2 - 2x + 4y + 4z + 8 = 0


20.

The ratio in which the sphere x2 + y2 + z2 = 504 divides the line segment AB joining the points A(12, - 4, 8) and B(27, - 9, 18) is given by

  • 2 : 3 externally

  • 2 : 3 internally

  • 1 : 2 externally

  • None of these


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