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Mathematics 16 Online
OpenStudy (4meisu):

Help with vectors please! Consider two unit vectors u and v, where u x v = -1. Look at all the linear combinations of u and v; {au + bv : a, b element of Real numbers} Which geometrical object(s) (eg. point, plane, circle) does this set represent? Give a reasoned answer.

ganeshie8 (ganeshie8):

Are you really sure that is a x product ?

OpenStudy (4meisu):

Hi ganeshi, this is what the problem looks like:

ganeshie8 (ganeshie8):

It is a \(\bullet\) product Not \(\times\) product Those two symbols have different meanings in vector algebra

OpenStudy (4meisu):

Got it, thanks

ganeshie8 (ganeshie8):

Remember the formula for dot product ?

OpenStudy (4meisu):

Yes. I have found that x = pi, though I'm not sure what this means in terms of a geometrical object.

ganeshie8 (ganeshie8):

How do the vectors look like when the angle between them is 180 ?

OpenStudy (4meisu):

Not sure. A straight line?

ganeshie8 (ganeshie8):

Yes Can u draw two vectors that have 180 degrees between them?

OpenStudy (4meisu):

Yes

ganeshie8 (ganeshie8):

Draw them here

OpenStudy (4meisu):

Wait that means that they are parallel

ganeshie8 (ganeshie8):

They are in opposite directions

ganeshie8 (ganeshie8):

Take one of them and multiply it by a number and think of the vector that u get

ganeshie8 (ganeshie8):

Multiplying a vector by a number only scales the vector. It doesn't change the direction

OpenStudy (4meisu):

So am I right in saying that the geometric shape is a straight line

ganeshie8 (ganeshie8):

Yep a straight line

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