# What is the angle between #<9,7,1># and #<8,3,6> #?

##### 1 Answer

Mar 2, 2016

#### Explanation:

The angle

#vec u = < 9,7,1># and#vec v = <8,3,6>#

can be computed with the formula

#cos alpha = (vec u * vec v ) / (|| vec u || * || vec v ||)#

where the product in the numerator is a dot product.

In your case, this means:

# cos alpha = (9 * 8 + 7 * 3 + 1 * 6) / (sqrt(9^2 + 7^2 + 1^2) * sqrt(8^2 + 3^2 + 6^2)) = (99)/(sqrt(131)*sqrt(109)) ~~ 0.8285#

Thus,

#alpha ~~34.06^@#