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NDA2013MathematicsThree Dimensional GeometryActual

What is the sum of the squares of direction cosines of x -axis?

Options

  1. A0
  2. B1 3
  3. C1
  4. D3

Correct answer

C. 1

Step-by-step solution

Angle made by x -axis with x -axis, y -axis and z -axis are 0^ , 90^ & 90^ respectively, therefore its direction cosines are (0^ ), (90^ ), (90^ ) i.e., 1,0,0 . Sum of the square of direction cosines =(1)^2+(0)^2+(0)^2=1

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