Check my work regarding vector projection?

**Mattpd** · June 30th 2010, 03:47 PM

Sorry if this is the wrong section, but it came from my Calc book.

Given: $a = 3i - 4j - k$ and $b = 2i + 5k$

Are these answers correct?

a) a dot b = 1
b) component of a in the direction of b = $1/\sqrt{29}$
c) projection of a in the direction of b = < 2/29, 0, 5/29 >
d) component of b in the direction of a = $1/\sqrt{26}$
e) projection of b in the direction of a = < 3/26, -2/13, -17/26 >

**Silverflow** · July 4th 2010, 02:11 AM

a) Yes, you are correct.

b) Correct.

c) Correct.

d) Again, correct

e) I'm not entirely sure how you obtained those numerators. I found the vector projection to be $b_{a}=\frac{3}{26}\vec{i} -\frac{4}{26}\vec{j}-\frac{1}{26}\vec{k}$ , using the formula $b_{a}=\frac{a \bullet b}{|b|^2}a$ . Using the same formula, you're answer to c is right. So, I'm not sure what you did. Feel free to point out something I did wrong.

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