1.

\[1+\cos \,{{56}^{o}}+\cos \,{{58}^{o}}-\cos {{66}^{o}}=\] [IIT 1964]

A. \[2\,\cos {{28}^{o}}\,\cos \,{{29}^{o}}\,\cos \,{{33}^{o}}\]
B. \[4\,\cos {{28}^{o}}\,\cos \,{{29}^{o}}\,\cos \,{{33}^{o}}\]
C. \[4\,\cos {{28}^{o}}\,\cos \,{{29}^{o}}\,\sin {{33}^{o}}\]
D. \[2\,\cos {{28}^{o}}\,\cos \,{{29}^{o}}\,\sin \,{{33}^{o}}\]
Answer» D. \[2\,\cos {{28}^{o}}\,\cos \,{{29}^{o}}\,\sin \,{{33}^{o}}\]


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