# Find U dot V

• Feb 25th 2014, 06:27 AM
IStandAlone99
Find U dot V
Find U ● V, angle between them is 55°, |u| = 6, |v|=4. I was wondering how to set this up, thanks.
• Feb 25th 2014, 06:41 AM
HallsofIvy
Re: Find U dot V
One fairly standard definition of the dot product of u and v is $\displaystyle |u||v| cos(\theta)$ where $\displaystyle \theta$ is the angle between the vectors. Have you not seen that before?
• Feb 25th 2014, 06:44 AM
IStandAlone99
Re: Find U dot V
I have not.
• Feb 25th 2014, 12:15 PM
sakonpure6
Re: Find U dot V
The dot vector http://www.mathsisfun.com/algebra/ve...t-product.html
This is the geometric dot vector because the definition has cos theta in it: $\displaystyle a \cdot b = |b| |a| cos \theta$
This is the algebraic dot vector, Let vector a=(x,y,z) b = (m,n,o) : $\displaystyle a \cdot b = (x,y,z) (m,n,o) \\= x*m + y*n + z*o$
Also you should note that the dot vector of any two vectors produces a SCALAR.

So provided the information and equation, can you solve the problem you have?
• Feb 25th 2014, 03:47 PM
Prove It
Re: Find U dot V
Quote:

Originally Posted by sakonpure6
The dot vector Dot Product
This is the geometric dot vector because the definition has cos theta in it: $\displaystyle a \cdot b = |b| |a| cos \theta$
This is the algebraic dot vector, Let vector a=(x,y,z) b = (m,n,o) : $\displaystyle a \cdot b = (x,y,z) (m,n,o) \\= x*m + y*n + z*o$
Also you should note that the dot vector of any two vectors produces a SCALAR.

So provided the information and equation, can you solve the problem you have?

It is NOT the dot vector. It is either called the DOT PRODUCT or the SCALAR PRODUCT. The result is a scalar, not a vector, and the vector product is different. Please use the correct terminology to avoid confusing the OP.
• Feb 25th 2014, 04:55 PM
sakonpure6
Re: Find U dot V
Thanks for noticing that, I meant "dot product".