derivative of cos(pi/4)

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Please find below the solution to the asked query:

$$\begin{gathered} \cos \left(\frac{\mathrm{\pi }}{4}\right)=\frac{1}{\sqrt{2}}=\mathrm{Constant} \mathrm{value} \\ \mathrm{We} \mathrm{know} \mathrm{that} \\ \frac{\mathrm{d}}{\mathrm{dx}}\left(\mathrm{Constant}\right)=0 \\ \Rightarrow \frac{\mathrm{d}}{\mathrm{dx}}\left[\cos \left(\frac{\mathrm{\pi }}{4}\right)\right]=0 \\ \mathrm{i}.\mathrm{e}. \mathrm{derivative} \mathrm{of} \cos \left(\frac{\mathrm{\pi }}{4}\right) \mathrm{is} 0. \end{gathered}$$

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