| 1. \[{{\sin }^{2}}\theta +{{\sin }^{2}}\phi ={{\cos }^{2}}\psi \] |
| 2. \[{{\cos }^{2}}\theta +{{\cos }^{2}}\phi ={{\sin }^{2}}\psi \] |
| 3. \[{{\sin }^{2}}\theta +{{\cos }^{2}}\phi ={{\cos }^{2}}\psi \] |
| Which of the above is/are correct? |
A) 1 only
B) 2 only
C) 3 only
D) 2 and 3
Correct Answer: B
Solution :
[b] If a line makes angle \[\theta \], \[\phi \] and \[\psi \] with x, y, z axes respectively, then \[{{\cos }^{2}}\theta +{{\cos }^{2}}\phi +{{\cos }^{2}}\psi =1\] \[\Rightarrow {{\cos }^{2}}\theta +{{\cos }^{2}}\phi =1-{{\cos }^{2}}\psi \] \[\Rightarrow {{\cos }^{2}}\theta +{{\cos }^{2}}\phi ={{\sin }^{2}}\psi \] \[\therefore \] Statement (2) is correct.
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