Question

how to find the projection of a=(1,3) on b=(4,0,2) ??

Answer 1

a onto b eh... vector right? its the |a| cos(angle between)

Answer 2

really ? I know diff. formula!!

Answer 3

angle is not mentioned at all in the question

Answer 4

t = \(cos^{-1}(a.b/(|a||b|))\)

Answer 5

well, in order to know the length of the projection onto b you gotta know the angle between a and b

Answer 6

not the length ! it said just the vector that is proj.

Answer 7

vectors are length and direction...cant have vector without length right?

Answer 8

sure! but I'm using the dot product ,, (a.b/||b||^2) x b

Answer 9

ok...

Answer 10

<1,3,0>
<4,0,2>
-------
4+0+0 =4

Answer 11

aha ,, then ?

Answer 12

sqrt(10).sqt(20) = sqrt(200)

Answer 13

cos_1(4/sqrt(200)) is what id try

Answer 14

73.57 degrees is the angle between them...

Answer 15

but we already have the cos of that: 4/sqrt(200) lol

Answer 16

4sqrt(10)
-------------- = 4/sqrt(20) right? this is the length of a vector
sqrt(10).sqrt(20) that is parallel to b

Answer 17

b/|b| = unit vector of b; then *that to get the vector projection

Answer 18

aha that the answer I've found but in diff. way

Answer 19

but the problem that it's multiple choice Qs. and I didn't find the answer !!

Answer 20

<4,0,2> 4
------- * ----- :)
sqrt(20) sqrt20

Answer 21

whats the choices?

Answer 22

i get: <16/20 , 0 ,8/20> if im right lol

Answer 23

the answers are : <1,1> , <2,1> , <2,-1> , <1,2>

Answer 24

that's the answer I've got ! but it seems that its wrong !!!

Answer 25

well, then we misunderstood what it was asking for then :)

Answer 26

the question which is up there is the exact same ques. !!!!!

Answer 27

yeah, perhaps its the vector that I drew in green?

Answer 28

http://www.vitutor.com/geometry/vec/vector_projection.html

Answer 29

thanks allot for trying ..

Answer 30

a.b
--- * b
|b|^2

4/20 = 1/5<4,0,2> = <4/5,0,2/5> cant really see it being nuthin else

Answer 31

youre welcome :) good luck

Answer 32

yes! that's my opinion two !

Answer 33

thank you ..