Finding the Polar Area of two circles intersecting each other











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enter image description here



The equations for the two circles are:



$r=18cos{theta}$



$r=3$



$r_f= 9$ and $r_g=3$



I can see that I need to subtract the $r=3$ circle, however im not sure on how to get the boundaries of integration.
I set $18cos{theta} = 9$ and got $pi/3$ and $5pi/3,$ using these boundaries for the equation gives me a wrong number.



It seems like I need help on setting my boundaries. Thanks










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  • The equation should be $18cos(theta) = 3$
    – Christopher Marley
    Dec 1 at 3:25










  • Oh ya, because you are trying to find the point of intersection correct?
    – Daniel2233
    Dec 1 at 3:30










  • Yep! Then $cos(theta) = frac16$ and it gets ugly.
    – Christopher Marley
    Dec 1 at 3:31










  • Wow thats even uglier than I had before
    – Daniel2233
    Dec 1 at 3:33






  • 1




    Thanks for the help @ChristopherMarley I ended up getting the right answer, but it was definitely ugly.
    – Daniel2233
    Dec 1 at 3:35















up vote
0
down vote

favorite












enter image description here



The equations for the two circles are:



$r=18cos{theta}$



$r=3$



$r_f= 9$ and $r_g=3$



I can see that I need to subtract the $r=3$ circle, however im not sure on how to get the boundaries of integration.
I set $18cos{theta} = 9$ and got $pi/3$ and $5pi/3,$ using these boundaries for the equation gives me a wrong number.



It seems like I need help on setting my boundaries. Thanks










share|cite|improve this question
























  • The equation should be $18cos(theta) = 3$
    – Christopher Marley
    Dec 1 at 3:25










  • Oh ya, because you are trying to find the point of intersection correct?
    – Daniel2233
    Dec 1 at 3:30










  • Yep! Then $cos(theta) = frac16$ and it gets ugly.
    – Christopher Marley
    Dec 1 at 3:31










  • Wow thats even uglier than I had before
    – Daniel2233
    Dec 1 at 3:33






  • 1




    Thanks for the help @ChristopherMarley I ended up getting the right answer, but it was definitely ugly.
    – Daniel2233
    Dec 1 at 3:35













up vote
0
down vote

favorite









up vote
0
down vote

favorite











enter image description here



The equations for the two circles are:



$r=18cos{theta}$



$r=3$



$r_f= 9$ and $r_g=3$



I can see that I need to subtract the $r=3$ circle, however im not sure on how to get the boundaries of integration.
I set $18cos{theta} = 9$ and got $pi/3$ and $5pi/3,$ using these boundaries for the equation gives me a wrong number.



It seems like I need help on setting my boundaries. Thanks










share|cite|improve this question















enter image description here



The equations for the two circles are:



$r=18cos{theta}$



$r=3$



$r_f= 9$ and $r_g=3$



I can see that I need to subtract the $r=3$ circle, however im not sure on how to get the boundaries of integration.
I set $18cos{theta} = 9$ and got $pi/3$ and $5pi/3,$ using these boundaries for the equation gives me a wrong number.



It seems like I need help on setting my boundaries. Thanks







calculus area polar-coordinates






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share|cite|improve this question













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edited Dec 1 at 3:28









saulspatz

13.3k21327




13.3k21327










asked Dec 1 at 3:23









Daniel2233

133




133












  • The equation should be $18cos(theta) = 3$
    – Christopher Marley
    Dec 1 at 3:25










  • Oh ya, because you are trying to find the point of intersection correct?
    – Daniel2233
    Dec 1 at 3:30










  • Yep! Then $cos(theta) = frac16$ and it gets ugly.
    – Christopher Marley
    Dec 1 at 3:31










  • Wow thats even uglier than I had before
    – Daniel2233
    Dec 1 at 3:33






  • 1




    Thanks for the help @ChristopherMarley I ended up getting the right answer, but it was definitely ugly.
    – Daniel2233
    Dec 1 at 3:35


















  • The equation should be $18cos(theta) = 3$
    – Christopher Marley
    Dec 1 at 3:25










  • Oh ya, because you are trying to find the point of intersection correct?
    – Daniel2233
    Dec 1 at 3:30










  • Yep! Then $cos(theta) = frac16$ and it gets ugly.
    – Christopher Marley
    Dec 1 at 3:31










  • Wow thats even uglier than I had before
    – Daniel2233
    Dec 1 at 3:33






  • 1




    Thanks for the help @ChristopherMarley I ended up getting the right answer, but it was definitely ugly.
    – Daniel2233
    Dec 1 at 3:35
















The equation should be $18cos(theta) = 3$
– Christopher Marley
Dec 1 at 3:25




The equation should be $18cos(theta) = 3$
– Christopher Marley
Dec 1 at 3:25












Oh ya, because you are trying to find the point of intersection correct?
– Daniel2233
Dec 1 at 3:30




Oh ya, because you are trying to find the point of intersection correct?
– Daniel2233
Dec 1 at 3:30












Yep! Then $cos(theta) = frac16$ and it gets ugly.
– Christopher Marley
Dec 1 at 3:31




Yep! Then $cos(theta) = frac16$ and it gets ugly.
– Christopher Marley
Dec 1 at 3:31












Wow thats even uglier than I had before
– Daniel2233
Dec 1 at 3:33




Wow thats even uglier than I had before
– Daniel2233
Dec 1 at 3:33




1




1




Thanks for the help @ChristopherMarley I ended up getting the right answer, but it was definitely ugly.
– Daniel2233
Dec 1 at 3:35




Thanks for the help @ChristopherMarley I ended up getting the right answer, but it was definitely ugly.
– Daniel2233
Dec 1 at 3:35















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