If u v w 9 find u middot v and u middot w See the figure b

If |u| = |v| =|w| = 9, find u middot v and u middot w. See the figure below.

Solution

Since all sides are equal, traingle is equilateral and hence angle between any two sides is 60 degess.

So,

u.v= u*v*cos60 =9*9*(1/2)=40.5

Next

u.w= u*w*cos120 =9*9*(-1/2)= - 40.5