yay
derivitives
everything is taken derivitve in repsect to time
da/dt=10cm^2/s
alright
area=pir^2
da/dt=2pir dr/dt
10cm^2/s=2pir dr/dt
r=10
[tex]\frac{10cm^2}{sec}=2\pi 10cm\frac{dr}{dt}[/tex]
[tex]\frac{10cm^2}{sec}=20\pi cm \frac{dr}{dt}[/tex]
divide both sides by 20pi
[tex]\frac{10cm^2}{20cm \pi sec}= \frac{dr}{dt}[/tex]
[tex]\frac{1cm}{2\pi sec}= \frac{dr}{dt}[/tex]
the rate of change of the radius when radius=10 is [tex]\frac{1cm}{2\pi sec}[/tex]
