Given:
[tex]\cos \frac{4\pi}{7}\cos \frac{11\pi}{42}-\sin \frac{4\pi}{7}\sin \frac{11\pi}{42}[/tex]The sum and difference formula is defined as,
[tex]\begin{gathered} \text{Cos(A}+B)=\cos \text{ A cos B-SinA sinB} \\ \text{Here, A= }\frac{\text{4}\pi}{7}\text{ and B=}\frac{11\pi}{42} \end{gathered}[/tex]So, for the given expression,
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