A) \[45{}^\circ \]
B) \[60{}^\circ \]
C) \[75{}^\circ \]
D) \[30{}^\circ \]
Correct Answer: A
Solution :
\[{{\cos }^{2}}\alpha =1-{{\cos }^{2}}{{60}^{o}}-{{\cos }^{2}}{{60}^{o}}\] \[=1-\frac{1}{4}-\frac{1}{4}=\frac{1}{2}\] Þ \[\alpha ={{45}^{o}}.\]
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