A) \[30{}^\circ \]or \[60{}^\circ \]
B) \[60{}^\circ \]or \[90{}^\circ \]
C) \[90{}^\circ \]or \[120{}^\circ \]
D) \[60{}^\circ \]or \[120{}^\circ \]
Correct Answer: D
Solution :
Given \[\alpha ={{45}^{o}},\,\,\beta ={{60}^{o}},\,\,\gamma =?\] \[\because \,\,\,{{\cos }^{2}}\alpha +{{\cos }^{2}}\beta +{{\cos }^{2}}\gamma =1\] \[\therefore \,\,\,{{\cos }^{2}}\gamma =1-\frac{1}{2}-\frac{1}{4}=\frac{1}{4}\,\,\Rightarrow \,\,\gamma ={{60}^{o}}\] or \[{{120}^{o}}\].
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