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MordecaiRocks 04/20/18 6:16:58 PM #1: |
This is probably pretty simple but I'm dumb, how do I calculate a cross product u x v if both u and v are given as cross products? Do I have to convert them back to vectors? Because I have no idea how to do that
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chill02 04/20/18 6:20:26 PM #2: |
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Eevee-Trainer 04/20/18 6:34:16 PM #3: |
You mind letting me see the problem @MordecaiRocks ? Not going to guarantee I have a solution but it's worth a shot because I *think* I have an idea of what you're getting at.
--- See me on Discord! ^.^ Eevee's Mystery Dungeon: https://discord.gg/V7hzcXd ... Copied to Clipboard!
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REMercsChamp 04/20/18 6:34:52 PM #4: |
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Buzz Killjoy 04/20/18 6:34:59 PM #5: |
I can draw a line if that's what you mean.
--- Does the name Pavlov ring a bell? ... Copied to Clipboard!
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Scotty_Rogers 04/20/18 6:35:24 PM #6: |
Linear algebra? Are you in 8th grade? lmao
--- Greatest debater on GameFAQs. My waifus Caulifla, Kale and Kefla from Dragon Ball Super and I drawn by da GOAT @MoistenedYouth: https://imgur.com/a/TYhlg ... Copied to Clipboard!
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MordecaiRocks 04/20/18 6:36:19 PM #7: |
Eevee-Trainer posted...
You mind letting me see the problem @MordecaiRocks ? Not going to guarantee I have a solution but it's worth a shot because I *think* I have an idea of what you're getting at. @Eevee-Trainer The problem is "Let u = 4i x 5j and v = j x k. Compute u x v and v x u" ... Copied to Clipboard!
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Scotty_Rogers 04/20/18 6:37:33 PM #8: |
REMercsChamp posted...
do your own fucking homework --- Greatest debater on GameFAQs. My waifus Caulifla, Kale and Kefla from Dragon Ball Super and I drawn by da GOAT @MoistenedYouth: https://imgur.com/a/TYhlg ... Copied to Clipboard!
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Eevee-Trainer 04/20/18 6:47:28 PM #10: |
I assume the i, j, and k have a little carat above their heads denoting the fact that they're unit vectors?
If so, remember that: * i-hat is the vector [1, 0, 0] * j-hat is the vector [0, 1, 0] * k-hat is the vector [0, 0, 1] Applying the scalar rule should get you 4i and 5j, and then you can find their cross product the normal way to find u. Similarly, find the cross product for v by the cross product of j-hat and k-hat. Then you can find u x v and v x u (though you'll want to note the property v x u = -(u x v) to save some time). Seems an unusually roundabout way to go about it though, thought for a second there might have been a typo in the thing. If you need help finding the cross product I can help with that too, though just know it's going to be the whole "find the determinant of a 3x3 matrix" way. --- See me on Discord! ^.^ Eevee's Mystery Dungeon: https://discord.gg/V7hzcXd ... Copied to Clipboard!
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DoGCyN 04/20/18 6:49:24 PM #11: |
Eevee, math major?
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Sariana21 04/20/18 6:50:00 PM #12: |
Scotty_Rogers posted...
Linear algebra? Are you in 8th grade? lmao Um, what? --- ___ Sari, Mom to DS (07/04) and DD (01/08) ... Copied to Clipboard!
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Eevee-Trainer 04/20/18 6:50:12 PM #13: |
DoGCyN posted...
Eevee, math major? Yup. Though linear algebra is a bit of a weak point and I don't think I've done cross products since like ... physics tbh. Kinda got them hammered into my head there though. --- See me on Discord! ^.^ Eevee's Mystery Dungeon: https://discord.gg/V7hzcXd ... Copied to Clipboard!
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frozenshock 04/20/18 6:51:21 PM #14: |
@MordecaiRocks
https://www.physicsforums.com/ They're going to be happy to help you. And probably better than most people here, too. --- I don't hate people, people hate me. ... Copied to Clipboard!
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awesome999 04/20/18 6:56:59 PM #15: |
Find u and v separately, then cross product again
u = 20k v = i u x v = 20j v x u = -20j Just remember that i x j = - j x i = k j x k = - k x j = i k x i = - i x k = j --- When it's kids, it's "bullying" but if it were adults, it's stalking, harassment, assault, criminal threats and just general abuse. -Tmk ... Copied to Clipboard!
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Eevee-Trainer 04/20/18 6:57:50 PM #16: |
awesome999 posted...
Just remember that *facepalm* I forgot about that being a thing. I just calculated it manually. --- See me on Discord! ^.^ Eevee's Mystery Dungeon: https://discord.gg/V7hzcXd ... Copied to Clipboard!
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AngelsNAirwav3s 04/20/18 6:57:57 PM #17: |
(A x B) x (C x D) = det(A,B,D) * C - det(A,B,C) * D
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Garioshi 04/20/18 6:58:37 PM #18: |
The cross product of two vectors is itself a vector. The cross product of two cross products is just another vector.
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MordecaiRocks 04/20/18 7:01:43 PM #19: |
@frozenshock
@Eevee-Trainer @awesome999 Thanks guys, appreciate it! Figured it wasn't as complicated as it seemed ... Copied to Clipboard!
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awesome999 04/20/18 7:03:36 PM #20: |
No problem, anything else?
--- When it's kids, it's "bullying" but if it were adults, it's stalking, harassment, assault, criminal threats and just general abuse. -Tmk ... Copied to Clipboard!
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MordecaiRocks 04/20/18 7:10:31 PM #21: |
awesome999 posted...
No problem, anything else? I'm good for now but I'm sure I'll get stuck on something again in the future lol ... Copied to Clipboard!
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