can you take dot product of different dimensions?

e.g. x=(9,2,4) y=3

Question

can you take dot product of different dimensions?

e.g. x=(9,2,4)  y=3

anonymous · Answer

I wonder because of problem a . (b.c) = (a.b) .c

loser66 · Answer

you can write y =(0,3,0) and then take product under the circumstance of x, y are vectors

anonymous · Answer

@Loser66 thanks for this suggestion :)

do you think a. (b.c) = (a.b) .c is a "trick question"? it looks like it asks about "commutative" in reality, it can't be multiplied like that?

loser66 · Answer

since the asker named that "dot product" I assume that those are vectors

anonymous · Answer

yes, a b c =vectors

but a.b gives a scalar?
then (a.b).c, would be scalar . c ?

loser66 · Answer

what makes you think the first dot is dot product (a$\bullet $b) and the second dot is a normal product (a.b)$\bullet$c but not a dot product?

loser66 · Answer

$a\bullet b$ = a scalar

anonymous · Answer

I thought they are all dot products

loser66 · Answer

take a look http://en.wikipedia.org/wiki/Dot_product

anonymous · Answer

thanks

so, it would only make sense if one of the dots is multiplication, right?
because can't dot product with a scalar

loser66 · Answer

yup

anonymous · Answer

ok thanks for the help :)

loser66 · Answer

np