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Mathematics 13 Online
OpenStudy (anonymous):

determine whether u and v are orthogonal, parallel, or neither

OpenStudy (anonymous):

u = <-5/3,7/2> v=<10,-21>

OpenStudy (anonymous):

its not neither and its not orthogonal SO IT IS PARALLEL BUT HOW DO i figure that out

OpenStudy (schrodingers_cat):

If the dot product between two vectors is zero they are perpendicular to each other. If they are multiples of each other they are parallel. If you want to solve for the angle between them use the defintion of the dot product which is, \[U .V = \left| U \right|\left| V \right|\cos \theta \] Just solve for theta. Hope this helps :)

OpenStudy (anonymous):

so i do the dot product and it is (-5/3)(10)+(7/2)(-21)=-541/6

OpenStudy (anonymous):

so that means they are not orthogonal. to find that they are parallel or neither u would find the angle in between? @Schrodingers_Cat

OpenStudy (schrodingers_cat):

Yes, they are not orthogonal and if they are not multiples of each other then are not parallel. So, check and see if they are multiples of each other :)

OpenStudy (anonymous):

how do u do that? we didn't learn that?

OpenStudy (schrodingers_cat):

Take the ratio of each components namely 10/(-5/3) = -6 -21/(7/2) = -6 Since its the same ratio they are multiples of -6 and are parallel. :)

OpenStudy (anonymous):

okay can u help with another?

OpenStudy (schrodingers_cat):

Sure :)

OpenStudy (anonymous):

given vectors u=<4,5> and v=<-5,-3> determine the quality indicated by (3u.2v)u

OpenStudy (schrodingers_cat):

So, you want (3U dot 2V)U correct?

OpenStudy (anonymous):

yes

OpenStudy (schrodingers_cat):

If so multiply vector U by 3 then vector V by 2. After that take the dot product between them and you will have a scalar value of which you just multiply U by. It will look like this \[((3(4)), (3(5)) . (2(-5),(2(-3))<4,5>\]

OpenStudy (anonymous):

which i did. the u on the outside would be the magnitude of u right?

OpenStudy (schrodingers_cat):

No, just the vector u.

OpenStudy (anonymous):

(12(-10) + 15(-6)) <4,5>?

OpenStudy (schrodingers_cat):

Yep looks right :)

OpenStudy (anonymous):

so then it would be (-210)<4,5>

OpenStudy (anonymous):

would that be your answer?

OpenStudy (schrodingers_cat):

Hope this helps :)

OpenStudy (anonymous):

that would be your answer though? @Schrodingers_Cat

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