A simple vector question

How would you do the last one ?

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look at the coordinates.

You have
A = (3,1,2) B = (2,2,-2)
D = (x,y,z) C = (5,-1,-2)

The differences between coordinate pairs will be the same, since they are on a rectangle.

e.g. A_z - B_z = 2 - (-2) = 4

i.e the difference between the z-coordinates for A and B is 4. So it will be the same for D and C, giving D_z = 2.

Ditto for the rest.

Reply 2

Ari Ben Canaan

Original post by steve10

I know that, but I want an algebraic method of finding it.

Reply 3

steve10

An alternative method would be to use the distance formula.
Both pairs of parallel sides are equal.
The two diagonals are equal.
You can then set up three simultaneous eqns and solve for the unknown coords of D.

That would take a bit more work, though.

Perhaps someone else has a quicker method.

Reply 4

ncsjohn02

just intersect the 2 lines CD and AD. this looks like HL math am i right?

Reply 5

Ari Ben Canaan

Original post by ncsjohn02

just intersect the 2 lines CD and AD. this looks like HL math am i right?

No its C4.

I'm looking for an algebraic method.

Reply 6

mintmocha

Think about it, when you draw it as a parallelogram you will realize that AB=DC right?
So, OD can also be said to be OC-AB, you can then proceed and you will get the answer. What paper is this i.e. which year?

Reply 7

electriic_ink

Original post by Ari Ben Canaan

I know that, but I want an algebraic method of finding it.

Why?

Reply 8

ncsjohn02

Original post by electriic_ink

Why?

hes probably too stupid/stubborn to do it the simplest way i.e. intersecting 2 lines, and wants to condense the method into a sub-form that he would understand. :rolleyes:

i.e. elementary algebra.

Reply 9

Ari Ben Canaan

Original post by ncsjohn02

hes probably too stupid/stubborn to do it the simplest way i.e. intersecting 2 lines, and wants to condense the method into a sub-form that he would understand. :rolleyes:

i.e. elementary algebra.

Lol.

By the way, I didnt neg your previous post.

Reply 10

ncsjohn02

Original post by Ari Ben Canaan

Lol.

By the way, I didnt neg your previous post.

i didnt say you did?

why are you telling me this. hmmm. :rolleyes:

Reply 11

Ari Ben Canaan

Original post by ncsjohn02

i didnt say you did?

why are you telling me this. hmmm. :rolleyes:

I thought this was some sort of childish tantrum you were throwing in retaliation for the neg rep you received.

I wouldnt put it beyond you...

Reply 12

ncsjohn02

Original post by Ari Ben Canaan

I thought this was some sort of childish tantrum you were throwing in retaliation for the neg rep you received.

I wouldnt put it beyond you...

oh i see. you happen to know me inside out eh? for one, i do not care about neg rep. 2, lying through your teeth on the internet still makes you a liar fyi. :rolleyes:

now about your topic. they say there is no such thing as a stupid question. i guess in your case there is.