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May 23rd, 2012, 11:25 PM   #1
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vector problems

http://i.imgur.com/j2jCo.jpg

can someone help me with this, & how do you solve vector problems?
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May 24th, 2012, 12:14 PM   #2
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Re: vector problems

1. I don't know how to draw something in 3 dimensions.

For 2 and 5 you need to know about dot products.

2. |B| = ?(B.B)

5. cos? = B.C/(|B||C|)

For 3. and 4., add vectors by adding components.
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May 24th, 2012, 02:57 PM   #3
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Re: vector problems

Quote:
Originally Posted by mathman
1. I don't know how to draw something in 3 dimensions.

For 2 and 5 you need to know about dot products.

2. |B| = ?(B.B)

5. cos? = B.C/(|B||C|)

For 3. and 4., add vectors by adding components.


for 4, i got ?3i+53j?16k , is that correct?
and for 5, i find the dot value and thats it?
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May 24th, 2012, 03:26 PM   #4
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Re: vector problems

4.
A = -4i + 3j + 9k
B = i + 8j - 2k
C = 14j - 9k

A - 3C + B

-4i + 3j + 9k - 3(14j - 9k) + i + 8j - 2k = -3i + 11j + 7k - 3(14j - 9k) = -3i + 11j + 7k - 42j + 27k = -3i - 31j + 34k.
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May 25th, 2012, 12:45 PM   #5
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Re: vector problems

For 5. you need to divide by the magnitudes of the vectors to get the cos of the angle.

B.C/(|B||C|), where |B| is compute like in 2. and |C| similarly.
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