f′(x) = (sec^2 x)etanx
Example 7: Find the second derivative of f (x) = ex
2
.
f′(x) = 2xex
2
f′′(x) = 2 ex
2
+ 4x^2 ex
2
Once again, it’s just a matter of following a formula.
THE DERIVATIVE OF loga x
This derivative is actually a little trickier than the derivative of a natural log. First, if you remember your
logarithm rules about change of base, we can rewrite loga x.
loga x =
Review the unit on Prerequisite Mathematics if this leaves you scratching your head. Anyway, because ln
a is a constant, we can take the derivative.
This leads us to our next rule.
Rule No. 5: If y = logax, then
Once again, incorporating the Chain Rule gives us a more useful formula.
Rule No. 6: If y = logau, then
Example 8: Find the derivative of f(x) = log 10 x.
f′(x) =