BITSAT2015MathematicsThree Dimensional GeometryActual
A line makes the same angle with each of the X and Z -axes. If the angle , which it makes with Y-axis, is such that ² =3 ² , then ² equals
Options
- A2 / 5
- B1 / 5
- C3 / 5
- D2 / 3
Correct answer
C. 3 / 5
Step-by-step solution
Let l, ~m and n be the direction cosines. Then, l= , m = , n = array l we have l²+m²+n²=1 ² + ² + ² =1 2 ² +1- ² =1 2 ² - ² =0 2 ² -3 ² =0 [ ² =3 ² 0( given ) ] ² =2 / 3 ² = 1 1+ ² = 1 1+2 / 3 = 3 5 array