Question
The derivative of $e^{ax} \cos bx$ with respect to $x$ is $r e^{ax} \cos \left( bx + \tan^{-1} \frac{b}{a} \right)$. When $a > 0$ and $b > 0$, the value of $r$ is ...
The derivative of $e^{ax} \cos bx$ with respect to $x$ is $r e^{ax} \cos \left( bx + \tan^{-1} \frac{b}{a} \right)$. When $a > 0$ and $b > 0$, the value of $r$ is ...