# How do I find the derivative of f(x)=pi^cosx?

The answer is: $y ' = {\pi}^{\cos} \left(x\right) \ln \left(\pi\right) \left(- \sin \left(x\right)\right)$
using the formula: $y = {a}^{f} \left(x\right) \Rightarrow y ' = {a}^{f} \left(x\right) \ln \left(a\right) f ' \left(x\right)$