Question

Which of the following vectors are orthogonal to (2,1)?

**choose ALL that apply!!!**

A. (-3,6)

B. (1,-2)

C. (-2,-3)

D. (1,2)

**a bit confused on this.. not too sure how to figure out if they are orthogonal :/ @terenzreignz :)

Answer 1

Dot product
I just mentioned that earlier ... YOU just mentioned that earlier...

Answer 2

\[v* u=0\]

Answer 3

haha oops :P

its not that ginormous equation thingy earlier right? :/

Answer 4

*from earlier

Answer 5

No, that was cross product, thank heavens we don't have to deal with that right now...
dot product of a pair of 2d vectors is far simpler...
<a , b> dot <c , d> = ac + bd

Answer 6

haha ohh okay :P

yay!

sooo 2(-3) + 1(6) = -6 +6 = 0

so A is a solution?

Answer 7

\[(x_1,y_1)* (x_2,y_2)=x_1x_2+y_1y_2\]

Answer 8

So,for instance, what's the dot product of
<2 , 1>
with
<-3 , 6>
?

Answer 9

2(1) + 1(-2) = 2 + (-2) = 2-2 = 0

so B is a solution also? :/

Answer 10

ermm -6 + 6 =0 ?

Answer 11

Yup.

As long as their dot product is zero, they are orthogonal (I'm pretty sure I already mentioned that :D )

Answer 12

ahh i see..

kk so we have A and B as solutions! lemme check the other two! :D

Answer 13

2(-2) + 1(-3) = -4 -3 = -7

so C is NOT an answer :P

Answer 14

2(1) + 1(2) = 2 + 2 =4

so again, nope!

so just A and B then! :)

Answer 15

GREAT :D

Answer 16

thanks!! :D

Answer 17

thanks!! :D