Question

PLZ help what is the angle between the vectors

a = (-9,8,-5)
b = (2,9,-9)

Answer 1

i keep getting 53.89 and that is incorrect

Answer 2

a dot b = |a|*|b|cos(theta)

Answer 3

so do the two vectors for the LHS then figure the magnitude of the each vector
and you will solve for

cos^(-1)((a dot b)/(|a||b|))

Answer 4

i keep doing that and i keep getting 53.89

Answer 5

i get 99/sqrt28220 every time

Answer 6

and you think that is wrong?

Answer 7

i know that is wrong my computer tells me so lol

Answer 8

yes i get 99/(2sqrt(7055))

Answer 9

sqrt(81+81+25) = sqrt(170)
sqrt(4+81+81) = sqrt(166)
sqrt(166)*sqrt(170) = 2sqrt(7055)

Answer 10

yeah that looks liek the same thing
sqrt(4*7055)

Answer 11

Yeah, I'm getting 53.8907 degrees too. Does it want the answer in radians?

Answer 12

does the book say 53.89?

Answer 13

o hmm

Answer 14

the book is wrong
http://www.wolframalpha.com/input/?i=the+angle+between+%3C-9%2C8%2C-5%3E+and+%3C2%2C9%2C-9%3E

Answer 15

what does the book say?

Answer 16

maybe it wants radians...

Answer 17

is it .94 @m.auld64 ?