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NDA2013MathematicsThree Dimensional GeometryActual

If is the acute angle between the diagonals of a cube, then which one of the following is correct?

Options

  1. A=30^
  2. B=45^
  3. C2 =1
  4. D3 =1

Correct answer

D. 3 =1

Step-by-step solution

If ' ' be the angle between the diagonals of a cube, then aligned ( ) & = 1(-1)+(-1)(1)+1(1) 1+1+1 1+1+1 & = -1 3 3 =- 1 3 & = ⁻¹ (- 1 3 )= ⁻¹ ( 1 3 ) aligned or, 3 ( )=1 .

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