Find the derivative of the following function.
f:x\longmapsto \dfrac{\cos\left(x\right)}{2^x}
f:x \longmapsto \dfrac{ \sin{\left(x\right)} } { \cos{\left(x\right)} }
f:x \longmapsto \dfrac{ \log_3{\left(x\right)} } {\sin{\left(x\right)}}
f:x \longmapsto \dfrac{e^{x} } {3^x}
f:x \longmapsto \dfrac{\ln{x} } {\log_2{x}}
f:x \longmapsto \dfrac{\ln{x} } {4^x}
f:x \longmapsto \dfrac{1/x } {\ln{\left(x\right)}}