${{\log }_{a}}b=\frac{{{\log }_{c}}b}{{{\log }_{c}}a}$ 
e.g. ${{\log }_{2}}5=\frac{{{\log }_{7}}5}{{{\log }_{7}}2}$ , ${{\log }_{11}}2=\frac{{{\log }_{p}}2}{{{\log }_{p}}11}$ Important notes: ${{\log }_{x}}y=\frac{1}{{{\log }_{y}}x}$


${{\log }_{a}}b=\frac{{{\log }_{c}}b}{{{\log }_{c}}a}$ 


e.g. ${{\log }_{2}}5=\frac{{{\log }_{7}}5}{{{\log }_{7}}2}$ , ${{\log }_{11}}2=\frac{{{\log }_{p}}2}{{{\log }_{p}}11}$
Important notes: 
${{\log }_{x}}y=\frac{1}{{{\log }_{y}}x}$

