Finding Boundaries of a Definition Area

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Homework Help Overview

The problem involves determining the boundaries for a double integral, specifically within the context of polar coordinates. The original poster describes the region defined by two circles and additional linear boundaries.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the conversion to polar coordinates and question the intersections of the defined boundaries. There is a focus on understanding the implications of the boundaries given by the equations and whether they intersect correctly.

Discussion Status

The discussion is ongoing, with participants exploring various interpretations of the boundaries and questioning the original poster's setup. Some guidance has been offered regarding the need to visualize the problem and consider the slopes of the lines involved.

Contextual Notes

There are indications that the original poster may have made typographical errors in the problem statement, which could affect the interpretation of the boundaries. The specific function being integrated has not been provided, leaving some ambiguity in the discussion.

Wi_N
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Homework Statement


Problem is part of a double integral. but my boundries are:

1<=x^2 + y^2 <=9 so between 2 circles with r1=1 and r2=3

and x<=y and y<=sqrt(3x)

the first boundary is obviously pi/4 and/or 3pi/4

the answer is pi/3 and i have no idea how u get that.

u obviously have to switch to polar coordinates but x=rcost y=rsint have no resulted in anything.
 
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Wi_N said:

Homework Statement


Problem is part of a double integral. but my boundries are:

1<=x^2 + y^2 <=9 so between 2 circles with r1=1 and r2=3

and x<=y and y<=sqrt(3x)

the first boundary is obviously pi/4 and/or 3pi/4
If you mean ##\theta = \frac \pi 4##, then yes, that is a boundary, but ##\theta = \frac {3\pi} 4## isn't a boundary.
Wi_N said:
the answer is pi/3 and i have no idea how u get that.
Nor do we, since you haven't told us what you're integrating or shown how you got your result.
Wi_N said:
u obviously have to switch to polar coordinates but x=rcost y=rsint have no resulted in anything.
Are you assuming that the line boundary and the quadratic boundary intersect on the outer circle?
 
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Wi_N said:

Homework Statement


Problem is part of a double integral. but my boundries are:

1<=x^2 + y^2 <=9 so between 2 circles with r1=1 and r2=3

and x<=y and y<=sqrt(3x)

the first boundary is obviously pi/4 and/or 3pi/4

the answer is pi/3 and i have no idea how u get that.
Have you drawn a picture including ##y =\sqrt 3 x##? What is its slope? Angle of inclination? That will tell you how to get ##\theta## for it.
 
Wi_N said:
y<=sqrt(3x)

LCKurtz said:
Have you drawn a picture including ##y =\sqrt 3 x##?
Per the OP, it is ##y \le \sqrt{3x}##, not ##y \le \sqrt 3x##.
 
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Mark44 said:
Per the OP, it is ##y \le \sqrt{3x}##, not ##y \le \sqrt 3x##.
I'm guessing that the OP mistyped the problem, especially in light of what he says the answer is supposed to be.
 
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LCKurtz said:
I'm guessing that the OP mistyped the problem, especially in light of what he says the answer is supposed to be.
Certainly within the realm of possibility.
 
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you guys are right. thnks.
 

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