Question

Let v= (5, -2) and w= (-10, 4). Which of the following is true? Check all that apply.

I think the answers are B. V*W=-58 and D. The y-component of w is 4.

Answer 1

how about A or C?

Answer 2

oh ok they might be better choices I am not exactly sure

Answer 3

well B and D are correct, but did you check out A or C?

Answer 4

I did but I am not sure about those two they did not look correct to me but maybe one of them is also?

Answer 5

are w and v perpendicular? if so, why?

if not, then why not?

Answer 6

think of the formula

\[\Large \cos(\theta) = \frac{ \vec{v}\cdot \vec{w}}{|\vec{v}|*|\vec{w}|}\]

Answer 7

@jim_thompson5910 im trying to figure it out using the formula but I am still having trouble with using this formula.

Answer 8

what must theta be if the vectors are perpendicular?

Answer 9

isn't θ is the angle between v ⃗ and w ⃗ .

Answer 10

yes it is

Answer 11

what must theta be if the vectors are perpendicular?

Answer 12

I know that to find a perpendicular vector the dot product must be 0.

Answer 13

that is correct, so in this case is v dot w = 0 ?

Answer 14

I looks to me no?

Answer 15

yes, it's actually -58

Answer 16

so the two vectors are NOT perpendicular

Answer 17

that rules out C, but what about A?

Answer 18

The way I would answer this I am not sure if this is right:

-2(5, -2)=(-10, 4) so I guess that would make A. an answer also?

Answer 19

A is correct as well

Answer 20

So A, B, D