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March 12th, 2017, 05:35 AM   #1
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Don't know what to do now

There is this equation: Θ(T)=V0Sin(2T)+Θ0Cos(2T)
It wants the time (T) where Θ will be 0. And say V0 and Θ0 has same value.
So I did this: V0 and Θ0 = X
0=Xsin(2t)+XCos(2t)
So I stop here: 0=X(Sin2T+Cos2T)
It also says to consider PI as 22/7.

Last edited by skipjack; March 12th, 2017 at 05:58 AM.
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March 12th, 2017, 05:57 AM   #2
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sin(2T) + cos(2T) ≡ √2sin(2T + $\pi$/4)
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March 12th, 2017, 06:43 AM   #3
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Quote:
Originally Posted by skipjack View Post
sin(2T) + cos(2T) ≡ √2sin(2T + $\pi$/4)
Sorry, still don't know what to do.

0=Sqrt(2)XSin(2T+ $\pi/$4)

0=Sqrt(2)XSin(2T+ (88/7))
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March 12th, 2017, 08:51 AM   #4
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$\pi/4$ isn't 88/7.

sin(2T + $\pi$/4) = 0 implies 2T + $\pi$/4 = k$\pi$, where k is an integer, so T = (k/2 - 1/8)$\pi$.
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March 12th, 2017, 09:06 AM   #5
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Quote:
Originally Posted by skipjack View Post
$\pi/4$ isn't 88/7.

sin(2T + $\pi$/4) = 0 implies 2T + $\pi$/4 = k$\pi$, where k is an integer, so T = (k/2 - 1/$\pi$.
I see, but the exercise requires a number as an answer, so there might be a way to eliminate de K. I said $\pi$4 is 88/7 because the exercise says to consider $\pi$ as 22/7
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