A) \[~{{120}^{o}}\] and \[{{300}^{o}}\]
B) \[~{{60}^{o}}\] and \[{{120}^{o}}\]
C) \[{{120}^{o}}\]and \[{{240}^{o}}\]
D) \[~{{60}^{o}}\] and\[~{{240}^{o}}\]
Correct Answer: C
Solution :
\[\cos \theta =-1/2,\]\[\cos 60=1/2,\,\cos \theta \]is negative in II and III quadrant, then \[\cos (180-60)=-\cos 60=-1/2\] \[\Rightarrow \]\[\theta =120,\cos (180+60)\] \[=-\cos 60=-1/2\Rightarrow \theta =240.\]
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