Quantcast Area between two curves Text - Physics Forums Library

PDA

View Full Version : Area between two curves


duki
Aug27-08, 11:15 PM
I have three questions:

1. The problem statement, all variables and given/known data

Find the areas of the regions whose boundaries are given.

2. Relevant equations

y=x^3-3
y=1

3. The attempt at a solution

x=-2, x=2
I got -10.67 but I know this can't be true because you can't have a negative area.



1. The problem statement, all variables and given/known data

Find the areas of the regions whose boundaries are given.

2. Relevant equations

y^2=x
x+y=2

3. The attempt at a solution

y=1, y=-2
I got -4.5, but again that can't be right because it's negative :(


1. The problem statement, all variables and given/known data

Find the areas of the regions whose boundaries are given.

2. Relevant equations

y=x^3-2x^2-3x
y=0

3. The attempt at a solution

I got to x=0, x=-1, and x=3 but I don't know where to go from here.

Thanks for any help! :)

Dick
Aug27-08, 11:29 PM
Let's just start with the first one. How did you get x=-2, x=2 or was that given? The curves y=x^3-3 and y=1 don't enclose any bounded region.

duki
Aug28-08, 12:06 AM
many apologies... it should have been x^2-3

HallsofIvy
Aug28-08, 05:52 AM
If you get a negative area then you have the two functions in the wrong order. For x between -2 and 2, the graph of x2- 3 is below the graph of y= 1. You should be integrating \int [1- (x^2-3)]dx= \int (4- x^2)dx. That, integrated between -2 and 2, is positive.

moemoney
Aug28-08, 08:50 AM
And for the last problem, you would have two different enclosed areas. One would be between -1 and 0 and the other between 0 and 3.
This means you would have to set up 2 different equations and find the sum of the areas.
HINT: The equations are very similiar just siwtched in order.