Evaluate the integral by interpreting it in terms of areas.

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Homework Help Overview

The discussion revolves around evaluating the integral of the function defined by the equation \( y = \sqrt{4 - x^2} \) over the interval from -2 to 2. Participants identify the geometric interpretation of the integral in terms of areas, specifically relating to a semicircle.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the identification of the area under the curve as a semicircle and question the inclusion of a rectangle in the area calculation. There is an exploration of similar problems and how their solutions were derived, prompting participants to reconsider their approach.

Discussion Status

The conversation is ongoing, with participants providing insights and questioning the assumptions made in the original poster's approach. Suggestions to sketch the graph have been made to clarify the area being evaluated, indicating a productive direction in the discussion.

Contextual Notes

Participants note that the original problem may have been misinterpreted by trying to apply techniques from a different problem that involved a rectangle. There is an emphasis on ensuring the similarity of problems before applying previous methods.

Hemolymph
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Homework Statement



from [-2,2] rad(4-x^2)

Homework Equations





The Attempt at a Solution


I know its a circle and i get the equation to be y^2+x^2=4

and I believe it has to be divided into a circle and rectangle
so the area of the rectangle i got to be 2
the circle i got to be 1/2(since its a half circle) times ∏(2)^2
the answer i got is
2+2pi (which is wrong) don't know where I went wrong tho.
 
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Hemolymph said:

Homework Statement



from [-2,2] rad(4-x^2)

Homework Equations





The Attempt at a Solution


I know its a circle and i get the equation to be y^2+x^2=4

and I believe it has to be divided into a circle and rectangle
so the area of the rectangle i got to be 2
the circle i got to be 1/2(since its a half circle) times ∏(2)^2
the answer i got is
2+2pi (which is wrong) don't know where I went wrong tho.

Where did the rectangle come from? It's just a semicircular area.
 
Curious3141 said:
Where did the rectangle come from? It's just a semicircular area.

I was doing a simliar problem of [-5,0] where it was evaluating 1+rad(25-x^2) dx
And the solution had a the area broken up into a rectangle and a semicircle
I guess i tried to apply the same technique to this problem.
The answer came out to be 5+(25pi)/4
 
Hemolymph said:
I was doing a simliar problem of [-5,0] where it was evaluating 1+rad(25-x^2) dx
The 1+ gave the rectangle there. You have no corresponding term here. Did you sketch the curve? Do you see a rectangle when you do?
 
Hemolymph said:
I was doing a simliar problem of [-5,0] where it was evaluating 1+rad(25-x^2) dx
And the solution had a the area broken up into a rectangle and a semicircle
When you're using what you found in a "similar" problem, make sure it's actually similar to the one you're working on.

As suggested by others in this thread, a quick sketch of the graph of x2 + y2 = 4 would show that your region is just the upper half of a circle.

Sketching a graph is usually the first thing you need to do in these problems.
Hemolymph said:
I guess i tried to apply the same technique to this problem.
The answer came out to be 5+(25pi)/4
 
Thanks for the advice/ help
 

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