How can I find the area inside two polar curves?

In summary, the conversation revolves around finding the area between two polar curves, r = sin(theta) and r = cos(theta). The speaker is struggling to set up the integral and asks for help. Another person suggests sketching the curves and utilizing symmetry to solve the problem. The conversation then delves into the specifics of integrating and multiplying to find the correct result. One speaker becomes confused and argues with the other, but eventually apologizes and asks for further assistance.
  • #1
G01
Homework Helper
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I need to find the area that's inside both of the following curves:

[tex] r = \sin\theta [/tex]

[tex] r = \cos\theta [/tex]

I know that I should have to subtract the area of the one curve from the other and I know the area formula for polar coordinates, but I just can't see how to set this one up any help or hints would be appreciated.
 
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  • #2
It's just two circles. the sin one is centered on the y-axis and the cos one is centered on the x axis. Sketch them and you will see what you have to do. Because of symmetry, you only need to integrate sin(t) from t=0 to t=pi/4 and multiply that integral by 2. Integrating cos(t) from t=pi/4 to t=pi/2 and then multiplying that integral by 2 will give you the same exact result.
 
  • #3
Shouldn't the area of sin t from 0 to pi/4 cover everything from the curve to the y axis. If you multiply that by 2 then you will end up with more area than what's in the loop won't you? I'm sorry I must be really confused
 
  • #4
No, that's 0 to pi/2. pi/4 is 1/8th of a circle
 
  • #5
these circles complete one rotation every pi degrees remember. So Pi/4 would be at the top of the circle with the cos and at the side of the sine circle.
 
  • #6
Dude, why are you arguing with me? I said that you integrate sin(t) from 0 to pi/4. If you don't think my answer is right, then don't use it.
 
  • #7
Im sorry, I think my explanation of this problem was bad I'm going to try to explain it again in another thread so I you still feel like halping me please go there.
 

1. What is the formula for finding the area inside two polar curves?

The formula for finding the area inside two polar curves is given by the double integral ∫∫r2−r1dθdr, where r1 and r2 are the two polar curves and θ is the angle of rotation.

2. How do I determine the limits of integration for finding the area inside two polar curves?

The limits of integration for finding the area inside two polar curves can be determined by finding the points of intersection between the two curves and using those points as the limits for the angle of rotation θ.

3. Can I use the formula for finding the area inside two polar curves for any type of polar curves?

Yes, the formula for finding the area inside two polar curves can be used for any type of polar curves as long as the limits of integration and the order of the curves are correctly determined.

4. Is there a graphical method for finding the area inside two polar curves?

Yes, the graphical method for finding the area inside two polar curves involves plotting the two curves on a polar coordinate plane and shading the region between the curves. The area can then be approximated by counting the number of grid squares within the shaded region.

5. Can I find the area inside two polar curves using calculus?

Yes, the formula for finding the area inside two polar curves involves using double integration, which is a calculus technique. However, the graphical method can also be used as an alternative for those who are not familiar with calculus.

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