Hey! I was recently trying to prove the derivative of a^x.
After trying it myself I ended up having to Google it because I don't seem to get it quite right. Here is what I tried to do:
y=ax
ln(y)=x∗ln(a)
ddxln(y)=ddxx∗ln(a)
Since ln(a) is a constant I just take the drivative of x which is one.
1y=ln(a)
From above we see that y = a^x so I substitute it in there.
1ax=ln(a)
Rearranging gives me:
1=ln(a)∗ax
Here comes my problem, the result is supposed to be:
dydx=ln(a)∗ax
the dy/dx is supposed to come up on the left hand side as I take the derivative of ln(y) and get 1/y. I don't understand why this happens and I haven't seen any explanation behind for that specific step. Everything else is logical, just logarithmic/exponential properties. I would appreciate any help, thanks in advance!
y = a^x take the ln of both sides
lny = lna^x and we can write
lny = ln a^x exponentiate both sides
e ^(ln y) = e^(ln a^x)
y = e^(ln a^x)
y = e^(x ln a) take the derivative
y ' = lna * e^(x ln a)
y ' = lna * e^(ln a^x)
y ' = lna * a^x and we can write
dy / dx = (ln a) * a^x