Suppose ω is a cube root unity with ω ≠&

Subject

Mathematics

Class

NDA Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

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1.

Suppose ω is a cube root unity with ω  1. Suppose P and Q are the points on the complex plane defined by ω and ω2. If O is the origin,then what is the angle between OP and OQ ?

  • 60°

  • 90°

  • 120°

  • 150°


A.

60°

C.

120°

From cube root of unity

ω =  - 1 + 3i2 and ω2 =  - 1 - 3i2

Projection of ωθ = tan-132 - 12 = tan-1 - 3θ = π - tan-1 - 3   = π - π3   = 2π3Projection of ω2α = tan-1 - 32 - 12 = π + tan-1 3α = π + π3   = 4π3So, angle between ω and ω2

   = 4π3 - 2π3 = 2π3 or = 120°


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2.

If x2 - px + 4 > 0 for all real values of x, then which one of the following is correct ?

  • p < 4

  • p  4

  • p > 4

  • p  4


3.

If z = x + iy = 12 - i2 - 25, where i =  - 1, then what is the fundamental amplitude of z - 2z - i2 ?

  • π

  • π2

  • π3

  • π4


4.

What is the range of the function y = x21 + x2

where, x  

  • [0, 1)

  • [0, 1]

  • (0, 1)

  • (0, 1]


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5.

A straight line intersects x and y axes at P and Q respectively. If (3, 5) is the middle point of PQ, then what is the area of the triangle OPQ ?

  • 12 square units

  • 15 square units

  • 20 square units

  • 30  square units


6.

If a circle of radius b units with centre at (0, b) touches the line y = x - 2, then what is the value of b ?

  • 2 + 2

  • 2 - 2

  • 22

  • 2


7.

Consider the function

fθ = 4sin2θ + cos4θ

What is the maximum value of the function f(θ)?

  • 1

  • 2

  • 3

  • 4


8.

Consider the function

fθ = 4sin2θ + cos4θ

What is the minimum value of the function f(θ)?

  • 0

  • 1

  • 2

  • 3


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9.

Consider the function

fθ = 4sin2θ + cos4θ

Consider the following statements :

1. fθ = 2 has no solution2. fθ = 72 has a solutionWhich of the above statements is/are correct ?

  • 1 only

  • 2 only

  • Both 1 and 2

  • Neither 1 nor 2


10.

Consider the curves

fx = xx - 1 and gx = 3x2, x > 02x,   x  0

Where do the curves intersect ?

  • At (2, 3) only

  • At ( - 1, - 2) only

  • At (2, 3) and ( - 1, 2)

  • Neither at (2, 3) nor at ( - 1,  - 2)


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