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## #1 2006-03-06 18:33:44

ganesh
Registered: 2005-06-28
Posts: 23,804

### Vectors

V # 1

Show that the vetcors a = (2,3,1), b = (5,-2,-4), and c = (10,-13,19) are mutually perpendicular.

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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## #2 2006-05-14 19:29:59

luca-deltodesco
Member
Registered: 2006-05-05
Posts: 1,470

### Re: Vectors

a dot b = cosine of angle between them, cosine of 90 degrees is 0, so if a dot b is 0, they are perpendicular

a dot b = 2*5 + 3*-2 + 1*-4 = 10-6-4 = 0, a,b are perpendicular
a dot c = 2*10 + 3*-13 + 1*19 = 20 - 39 + 19 = 0, a,c are perpendicular
b dot c = 5*10 + -2*-13 + -4*19 = 50 + 26 - 76 = 0, b,c, are perpendicular

Last edited by luca-deltodesco (2006-05-14 19:30:45)

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The End Of All Things To Come.

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## #3 2006-05-14 20:09:28

ganesh
Registered: 2005-06-28
Posts: 23,804

### Re: Vectors

Very well done, luca-deltodesco!

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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## #4 2007-06-09 02:31:28

angel_12
Member
Registered: 2007-06-07
Posts: 4

### Re: Vectors

waise that was a bit easy one!

Nothing is impossible..even impossible says I'm possible!

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## #5 2007-11-06 09:16:27

mikau
Member
Registered: 2005-08-22
Posts: 1,504

### Re: Vectors

i'd like to demand lots of vector proof problems, please!

can't find enough of them.

A logarithm is just a misspelled algorithm.

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## #6 2011-12-28 04:17:02

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,037

### Re: Vectors

hi ganesh

only one problem??? o.O

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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