Evaluate the following: 47^ 13^ - 47^ 13^ - Vidyadip

Question

Evaluate the following: $\cos47^\circ\cos13^\circ-\sin47^\circ\sin13^\circ$

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Answer

$=\cos(47^\circ+13^\circ)$ $[\cos(\text{A+B})=\cos\text{A}\cos\text{B}-\sin\text{A}\sin\text{B}]$ $=\cos60^\circ$ $=\frac{1}{2}$

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