dA = 2 pi r dr
yes, correct
however notice that this is simply the circumference
the new area added is the circumference * dr
The circular area A in square centimetres of a healing wound is given by
A(r)=πr^2
Where r =the radius in centimetres. Find the rate of change of the area with respect to the radius.
My work:
I'm not really sure if this is correct but I gave it a try.
Dy/dx =π*2r^2-1
= 6.283r
3 answers
I'm very confused ?
Yes
dA/dr = 2 pi r = 6.28 r
correct
however think a little more
dA = 2 pi r dr = circumference * dr
If you draw a picture of a circle r and then one outside it with radius r + dr
You will see immediately that the change in area is the strip of length 2 pi r times the width dr
dA/dr = 2 pi r = 6.28 r
correct
however think a little more
dA = 2 pi r dr = circumference * dr
If you draw a picture of a circle r and then one outside it with radius r + dr
You will see immediately that the change in area is the strip of length 2 pi r times the width dr
1 answer