# Thread: Check my work regarding vector projection?

1. ## Check my work regarding vector projection?

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

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

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 >

2. 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.