A) \[60{}^\circ \]
B) \[120{}^\circ \]
C) \[60{}^\circ \,\,\text{or}\,\,120{}^\circ \]
D) None of these
Correct Answer: A
Solution :
Let \[\gamma \]is the required, angle, then \[{{\cos }^{2}}45{}^\circ +\cos {}^\circ 60{}^\circ +{{\cos }^{2}}\gamma =1\] \[\Rightarrow \]\[\frac{1}{2}+\frac{1}{4}+{{\cos }^{2}}\gamma =1\] \[\Rightarrow \]\[{{\cos }^{2}}\gamma =1-\frac{3}{4}=\frac{1}{4}\] \[\Rightarrow \]\[\cos \gamma =\frac{1}{2}\] \[\Rightarrow \] \[\gamma =60{}^\circ \]
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