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#1 2006-12-13 21:48:50
- RauLiTo
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- From: Bahrain
- Registered: 2006-01-11
- Posts: 142
inner product
hi guys ... how are you ?!
if you know that : || L || = 4 ... || 2 L + M || = 13 ... the angle between the two vectors is θ = 120 ... what is the inner product of these two vectors ?! it looks easy but i dont know why they told me that my answer is wrong which was - 10 or 42 
help please ...
ImPo$$!BLe = NoTH!nG
Go DowN DeeP iNTo aNyTHinG U WiLL FinD MaTHeMaTiCs ...
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#2 2006-12-14 04:09:09
- luca-deltodesco
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Re: inner product
inner product = dot product i think in which case
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#3 2006-12-14 04:44:54
- RauLiTo
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Re: inner product
no man i meant with the two vectors L and M ... we have L but we have to get M first
ImPo$$!BLe = NoTH!nG
Go DowN DeeP iNTo aNyTHinG U WiLL FinD MaTHeMaTiCs ...
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#4 2006-12-14 04:52:31
- luca-deltodesco
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Re: inner product
oooh, you mean the product of L and M, not L and 2L+M 
well then from that same equation i had
Last edited by luca-deltodesco (2006-12-14 04:54:28)
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#5 2006-12-14 05:11:56
- RauLiTo
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Re: inner product
theta is the angle between L and M so we cant use it to get the first equation you said
ImPo$$!BLe = NoTH!nG
Go DowN DeeP iNTo aNyTHinG U WiLL FinD MaTHeMaTiCs ...
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#6 2006-12-14 07:08:23
- luca-deltodesco
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Re: inner product
ah... lol
Last edited by luca-deltodesco (2006-12-14 07:09:03)
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#7 2006-12-14 16:32:40
- RauLiTo
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Re: inner product
guys ?!
ImPo$$!BLe = NoTH!nG
Go DowN DeeP iNTo aNyTHinG U WiLL FinD MaTHeMaTiCs ...
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#8 2006-12-14 17:32:35
- Stanley_Marsh
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Re: inner product
I think you can draw a graph about it , 2L+M connect the two point of a parallelogram consists by M and 2L , knowing the length of 2L , and 2L+M ,and the angle , use geometry to solve it
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#9 2006-12-15 06:50:40
- RauLiTo
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Re: inner product
the final answer is - 30 ... anybody ?
ImPo$$!BLe = NoTH!nG
Go DowN DeeP iNTo aNyTHinG U WiLL FinD MaTHeMaTiCs ...
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#10 2006-12-15 07:19:24
- luca-deltodesco
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Re: inner product
ok so we have
//quadratic in |M|
//+ is taken over -, since - would give a negative length to M, which is not allowed
Last edited by luca-deltodesco (2006-12-15 20:05:45)
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#11 2006-12-15 20:03:13
- RauLiTo
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Re: inner product
thaaaaanks 
btw its not 106 its 105
thans again
ImPo$$!BLe = NoTH!nG
Go DowN DeeP iNTo aNyTHinG U WiLL FinD MaTHeMaTiCs ...
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#12 2006-12-15 20:04:51
- luca-deltodesco
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Re: inner product
thaaaaanks
thans again
i corrected in my working out
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