# Math Help - Differentiation (2)

1. ## Differentiation (2)

Q:

A rocket, R, rises vertically from a point A on ground level. It is observed from another point B on the ground, where B is 10 km from A. When the angle of elevation has the value pi/4 radians, this angle is increasing at the rate of 0.005 radians per second. Find, in m/s, the velocity of the rocket at that instant.

Thank you for helping!

2. We must find dy/dt given x=10, $\frac{d{\theta}}{dt}=\frac{1}{200}, \;\ {\theta}=\frac{\pi}{4}$

$\frac{y}{10}=tan{\theta}$

Differentiate:

$\frac{dy}{dt}=10sec^{2}{\theta}\frac{d{\theta}}{dt }$

Plug in your knowns and you're all set.