# If #veca = << 2,4,-1 >>#, #vecb = << 6,1,2 >># and #vecc = veca - vecb#, what is the angle between #veca# and #vecc#?

##### 1 Answer

Jul 11, 2016

#### Explanation:

#= <2,4,-1> - <6,1,2 >#

#= <-4,3,-3>#

Using that for two vectors

#=(<2,4,-1> * <-4,3,-3>)/(sqrt(2^2+4^2+(-1)^2)*sqrt((-4)^2+3^2+(-3)^2)#

#=(2(-4)+4(3)+(-1)(-3))/(sqrt(21)*sqrt(34)#

#=7/sqrt(714)#