A) \[1\]
B) \[0\]
C) \[-1\]
D) \[\frac{1}{2}\]
Correct Answer: A
Solution :
\[\sin {{20}^{o}}\cos {{70}^{o}}+\cos {{20}^{o}}\sin {{70}^{o}}\]\[=({{90}^{o}}-{{70}^{o}}).\cos {{70}^{o}}+\]\[\cos ({{90}^{o}}-{{70}^{o}})\sin {{70}^{o}}\] \[={{\cos }^{2}}{{70}^{o}}+{{\sin }^{2}}{{70}^{o}}=1\]
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