The vectors and are perpendicular. Find k .

Question

The vectors <8,4> and <8,k> are perpendicular. Find k .

amistre64 · Answer

do a dot product to solve for k

amistre64 · Answer

or, swap the first one, and negate an element and scale it ...

amistre64 · Answer

type in the reply box down here to respond in a post ....

amistre64 · Answer

how what?  dot product?  or a perp property?

anonymous · Answer

any of them that's easier?
what is the answer ?

amistre64 · Answer

we dont give out direct answers; we try to help you approach a solution.

You must have come across something in your material that relates to this.  Im just assuming you have heard of a dot product; or have been exposed to the perpendicular slope property

anonymous · Answer

none, im doing the aleks prgram as a pre req for my physiqs ,

anonymous · Answer

i assume the answer would be -4 isn't it?

amistre64 · Answer

i like -4 as an answer.  just not too sure how you approached it :)

anonymous · Answer

according to here... http://mathworld.wolfram.com/PerpendicularVector.html

amistre64 · Answer

for a dot product, I stack the vectors and multiply down the columns <8,4> <8,k> ------ 64+4k <-- then add the row perp vectors have a dot product that is equal to 0 64+4k = 0 4k = -64 k = -8 ; hmm, im liking -8 better than -4 at the moment

amistre64 · Answer

pfft, i spose the test i just got out of took a toll on me ....

amistre64 · Answer

-64/4 = -16  :)

the perpendicular slope property would have given us this
$$\frac48\frac k8=-1$$
$$\frac4{64}k=-1$$
$$k=-\frac{64}{4}$$
as well

anonymous · Answer

ok thanks

amistre64 · Answer

... now i have to worry about that test lol