y() = e sin(8)
for this one i got 8e^(theta)*cos(8theta)...
but it was wrong, what did i do wrong??
Hello, mathaction!
Have you forgotten the Product Rule?
$\displaystyle y \:=\:e^{\theta}\!\cdot\!\sin(8\theta)$
We have: .$\displaystyle \frac{dy}{d\theta} \;=\;e^{\theta}\cdot\cos(8\theta)\cdot8 + e^{\theta}\cdot\sin(\theta) \;=\;e^{\theta}\left[8\cos(8\theta) + \sin(\theta)\right] $