integrating a parametric question Watch

theweirdo
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x=5cost y=3sin2t

need to integrate -15sin^2tcost
-the limits for x are 5 and 0.
-I changed the limits to 0 and pi/2
-Got 5 as my final answer, but the answer is 10?
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mqb2766
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Could you upload your working?
(Original post by theweirdo)
x=5cost y=3sin2t

need to integrate -15sin^2tcost
-the limits for x are 5 and 0.
-I changed the limits to 0 and pi/2
-Got 5 as my final answer, but the answer is 10?
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theweirdo
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(Original post by mqb2766)
Could you upload your working?
Yup
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I'm God
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(Original post by theweirdo)
Yup
Assuming you used the double angle formula for sin2t in the third line, I think you didn't multiply the 15 by 2
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GreenDeath
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(Original post by theweirdo)
x=5cost y=3sin2t

need to integrate -15sin^2tcost
-the limits for x are 5 and 0.
-I changed the limits to 0 and pi/2
-Got 5 as my final answer, but the answer is 10?
Is it because you are meant to multiply your answer by 2 because you found the area above the x-axis only? can you upload the full question please.
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theweirdo
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(Original post by GreenDeath)
Is it because you are meant to multiply your answer by 2 because you found the area above the x-axis only? can you upload the full question please.
yup, sure
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hahaweeb
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That's what I think OP did wrong as well.
(Original post by I'm God)
Assuming you used the double angle formula for sin2t in the third line, I think you didn't multiply the 15 by 2
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theweirdo
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(Original post by I'm God)
Assuming you used the double angle formula for sin2t in the third line, I think you didn't multiply the 15 by 2
omg yes i did forget to do that!
i didn't see that! i'll try the question again
thank you
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B0redBrioche
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Same should be -30sin^2tcost
(Original post by hahaweeb)
That's what I think OP did wrong as well.
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theweirdo
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(Original post by B0redBrioche)
Same should be -30sin^2tcost
(Original post by hahaweeb)
That's what I think OP did wrong as well.
(Original post by I'm God)
Assuming you used the double angle formula for sin2t in the third line, I think you didn't multiply the 15 by 2
tried this and it worked thank you!
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I'm God
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(Original post by theweirdo)
tried this and it worked thank you!
Nice! :top:
No worries mate
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