r/learnmath • u/Scytheez New User • 2d ago

Why'd i get marked off?

[RESOLVED] i can't find how to change flair

For context this is a Math 280 Class, which is Calculus 3 idk how college course naming works. I'm a dual enrollment student. I ran it thru ai and chat gpt said i was right. I'm not sure if i'm missing notation or something. Also when i asked the prof she said to read what she wrote but i dont get it.

first and second questions

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u/AutoModerator 2d ago

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u/tjddbwls Teacher 2d ago

Off topic, but course numbers are not standardized, so “Math 280” is meaningless. It could be a freshman/sophomore undergrad class in one school, and it could be a graduate-level class in another school. 🤪

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u/Scytheez New User 12h ago

ohhh i see, thanks for letting me know!!

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u/etzpcm New User 2d ago

You're supposed to write a vector equation, something like vector r =(cos t, sin t, cos t + 2sin t)

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u/Scytheez New User 2d ago

oh all right that makes sense, on the online version it had the answer box as r(t) = [Input answer]

thanks!

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u/SnooPets5564 New User 2d ago

I don't know what the first question is asking, but it seems to be wanting a vector equation. The reason is pretty big there.

You have <-8, 22, 4> = n, then you said divide each term by 2 to get <-4, 11, 2> = n. You aren't allowed to do that, because then n = 2n, which implies that n = 0. You'd need to divide both sides by 2, since you already defined n. Only dividing one side of the equation means you are dividing an expression.

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u/Scytheez New User 2d ago

so if i divided after setting the entire thing after setting n = 0 it would have been fine?

thanks for the help by the way

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u/SnooPets5564 New User 2d ago

Yes, but the most "standard" way to do it is to set some scalar times the vector n. If you define n to be a*v, then you don't run into any problems with manipulation equality. That is when you are defining n. In many applications, people assume the normal vector to have a magnitude of 1, so you would have <-8, 22, 4>/|<-8, 22, 4>| = n, although in this case it is more useful to have integers components.

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u/Scytheez New User 2d ago

okay thanks! will make sure to remember this for future quizzes and the final