A) 0
B) 1
C) 2
D) \[\frac{3}{2}\]
Correct Answer: A
Solution :
\[\cos \,\,{{52}^{o}}+\cos \,\,{{68}^{o}}+\cos \,\,{{172}^{o}}\] \[=(\cos \,\,{{52}^{o}}+\cos \,\,{{172}^{o}})+\cos \,\,{{68}^{o}}\] \[=2\,\,\cos \,\,{{112}^{o}}\,\cos \,\,{{60}^{o}}+\cos \,\,{{68}^{o}}\] \[=\cos \,\,{{112}^{o}}+\cos \,\,{{68}^{o}}=2\,\,\cos \,\,({{90}^{o}})\,\,\cos \,\,{{22}^{o}}=0\].
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