MHT CET2018MathematicsStraight Lines
If a line makes angles 120 o and 60 o with the positive directions of X and Z axes respectively then the angle made by the line with positive Y - axis is
Options
- A150 o
- B60 o
- C135 o
- D120 o
Correct answer
C. 135 o
Step-by-step solution
cos 2 β = 1 − cos 2 α − cos 2 γ = 1 − cos 2 ( 120 o ) − cos 2 ( 60 o ) = 1 − 1 4 − 1 4 = 1 − 1 2 cos β = ± 1 2 β = 135 o , 45 o