A) \[{{30}^{o}}\]
B) \[{{60}^{o}}\]
C) \[{{75}^{o}}\]
D) \[{{45}^{o}}\]
Correct Answer: D
Solution :
Clearly, \[{{\cos }^{2}}\alpha +{{\cos }^{2}}{{60}^{o}}+{{\cos }^{2}}{{60}^{o}}=1,\] where \[\alpha \] is the angle which the straight line makes with \[x-\]axis, \[\therefore \] \[{{\cos }^{2}}\alpha =1-\frac{1}{4}-\frac{1}{4}=\frac{1}{2}\] \[\Rightarrow \] \[\cos \alpha =\frac{1}{\sqrt{2}}\] \[\Rightarrow \] \[\alpha ={{45}^{o}}\]
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