Question

If v1 = (2,4) and v2 = (-1,5), then v1 * v2 is equal to which of the following?

A. 22
B. 18
C. (8,-5)
D. (-2,20)

Answer 1

I am confused on whether or not I put my answer in parentheses or not. So it would be either B or D.

Answer 2

D. (-2,20)* >.>

Answer 3

Would we leave them in the parentese or add the vectors together?

Answer 4

Cross product of verctors, right?

Answer 5

It doesn't specify but that's what I am assuming.

Answer 6

Have they given you a figure or something?

Answer 7

Nope, just coordinates.

Answer 8

pretty sure then want dot product because none of those is cross

Answer 9

Here's what I found. I think the answer would be 18...

There is yet another operation associated with vectors. Given two vectors v1 = (x1,y1) and v2 = (x2,y2), the dot product of v1 and v2, written , is the scalar:

x1x2 + y1y2.

In other words, the dot product is obtained by multiplying corresponding coordinates of the two vectors and then adding the results.

Answer 10

So -2 + 20 = 18?

Answer 11

yes that is correct

Answer 12

for future ref, the cross product of 2 vectors will result in a vector that ins the direction that is perpendicular to both of the vectors in this case, the 2 vectors are in a plane <X,y> so the cross will exist completely in the Z direction <0,0,Z>