Calculus help

[goofyre 10+ year member]

So I have a test tomorrow and don't quite know how to solve these. If someone could explain how to do them, that would be fantastic. I don't necessarily need the answer just need to understand how to find it.

Find the projection of [-4,-2,0 onto [-5,-1,1].
Enter your answer in the form [x,y,z]

Find the orthogonal projection of [-1,1,-1] onto [-1,-1,2].
Enter your answer in the form [x,y,z].

Find a unit vector orthogonal to (3,1,-4) and (2,-3,3).
Enter your answer in the form [x,y,z].

Any help would be greatly appreciated.

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[dleccord 5,000+ posts]

how much money you got son?

 

[ArrizX 10+ year member]

Why ask? Not like you could do it anyways.

 

[ToyTundra 10+ year member]

the last one you take the cross product then divide by the magnitude. I dunno about the others.

 

[dleccord 5,000+ posts]

Why ask? Not like you could do it anyways.

Ah very clever of you to say that.

 

[JG903 10+ year member]

So I have a test tomorrow and don't quite know how to solve these. If someone could explain how to do them, that would be fantastic. I don't necessarily need the answer just need to understand how to find it.






Any help would be greatly appreciated.

You must be in Multivariate/Calculus III. I think I can help.

To find the projection in the first one it is

(dot product of the vectors / Magnitude of [-5,-1,1]) * (Vector [-5,-1,1] / Magnitude of [-5,-1,1])

Second one, to find the orthogonal, just do cross product.

Third on just like some said already take the cross product then divide by the magnitude