# Thread: Find the derivative of this Function.

1. ## Find the derivative of this Function.

I don't really know how to do this one, can someone please help me step by step, Thanks.

y=e^(cos+lnt)

= d/dx(e) + d/dx(cos+lnt)
= e + (-sin+lnt)
= e-sint

2. Originally Posted by Cyberman86
I don't really know how to do this one, can someone please help me step by step, Thanks.

y=e^(cos+lnt)

= d/dx(e) + d/dx(cos+lnt)
= e + (-sin+lnt)
= e-sint
Your equation makes no sense. cos of what? Is lnt = ln(t)?

3. hello
$\displaystyle \left (\exp(u) \right )'=u'\times\exp(u)$
put $\displaystyle u=\cos(t)+\log(t)$

4. Originally Posted by e^(i*pi)
Your equation makes no sense. cos of what? Is lnt = ln(t)?
That's how its written in the book.

y=e^(cos+lnt)

5. Originally Posted by Cyberman86
That's how its written in the book.

y=e^(cos+lnt)
there must be a typo
i think you meant (they meant) $\displaystyle y=\exp(\cos(t)+\ln(t)) =t\times \exp(\cos(t))$,in this case the derivative is,
$\displaystyle y'=\exp(\cos(t))-t\times\sin(t)\times\exp(\cos(t))$.
hope that helps.