Product of 2 vectors help

[gtfitzpatrick]

Homework Statement

r.k where r=xi+yj+zk

The Attempt at a Solution

is the answer to this just z or is it x+y

 

[cristo]

Well, why do you think it is either of the answers you quote?

What is the definition of the dot product of two vectors?

 

[gtfitzpatrick]

Dot product of 2 vectors a.b is a1b1+a2b2+a3c3?

 

[gtfitzpatrick]

i think k.k = 0

 

[cristo]

Dot product of 2 vectors a.b is a1b1+a2b2+a3c3?

Ok, good. So, presumably, this definition is for two vectors a=(a1,a2,a3) and b=(b1,b2,b3). Can you write your two vectors in this form?

i think k.k = 0

Hold on.. this doesn't agree with what you stated above. Have another think...

 

[gtfitzpatrick]

xi+yj+zk.k so this is x0+y0+z1 = z?

 

[cristo]

Yup, that's correct.

 

[gtfitzpatrick]

thanks a mill

 

[cristo]

No problem!