How do you find the approximate uncertainty of a circle of radius 3.8x10^4?

[steve snash]

how do you find the approximate uncertainty of a circle of radius 3.8x10^4?

Homework Statement

how do you find the approx uncertainty for a circle with radius 3.8x10^4, i have no idea how to get the final uncertainty of the circle the radius uncertainty is 0.1x10^4

area of a circle is pie*r^2? so that means the area of the circle should be 4.5x10^9 isn't it?

The Attempt at a Solution

i figured that because there is only one variable that the uncertainty would just be 0.1x10^4, how do you work out the final uncertainty properly?

 

[steve snash]

please help i need to know by tomorrow =p

 

[willem2]

One way to do this that always works is to calculate the area for the minimum and for the
maximum radius to find out what the minimum and maximum values of the area are.

Another way is $f(x+ e) \approx f(x) + e f'(x)$ is e is small. (e is the error)

 

[steve snash]

thanks willem, saved my life =)