Suppose a vector y is orthogonal to vectors u and v. Show that y is orthogonal to the vector u + v.
y.u=0 and y.v=0
(a.b=0 if a and b are orthogonal, a.b is the dot product of vectors)
y.(u+v) = y.u + y.v = 0+0 =0
( a.(b+c)=a.b + a.c beacuse dot product is distributive )