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AP EAMCET201824 Apr 2018Morning ShiftMathematicsThree Dimensional GeometryActual

If a line makes angles 4 and 3 with Y -axis and Z -axis respectively, then the obtuse angle made by that line with X -axis is

Options

  1. A3
  2. B2 3
  3. C6
  4. D5 6

Correct answer

B. 2 3

Step-by-step solution

Let line makes angle with X -axis then, direction cosine of the line are l= , m= 4 , n= 3 But l^2+m^2+n^2=1 gathered l^2+ ( 1 2 )^2+ ( 1 2 )^2=1 l^2+ 1 2 + 1 4 =1 l^2= 1 4 l= 1 2 gathered =- 1 2 ( is obtuse angle ) = - / 3=2 / 3 .

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