Wednesday, December 30, 2015

logarithms - Why is $ a^x = e^{x log a} $?




Why is $ a^x = e^{x \log a}$, where $ a $ is a constant?



From my research, I understand that the the natural log of a number is the constant you get when you differentiate the function of that number raised to the power $ x$. For example, if we differentiate the function $ 2^x $, we get $ 2 \log 2$. I also understand that the natural log of e is just 1. But I cannot connect the dots here.



I would really appreciate an intuitive explanation of why we can write a number raised to a power as e raised to (the power x the natural logarithm of the number)?


Answer



I think we can agree that



$$a=e^{\log a}$$




which arises from one of the properties of the logarithm. Therefore, it’s sufficient to say that



$$a^x=e^{\log a^x}$$



But one of the properties of the logarithm also dictates that



$$\log a^x=x\log a$$



Therefore




$$a^x=e^{x\log a}$$


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