Which of the vectors are Orthogonal?

Question

a = (1,2), b = (0,1), c = (−2,−4), u = (−2,1) , v = (2,4), w = (−6,3)

Answer 1

Vectors a, c, and v are orthogonal to u and w. The dot products such as a•u = -2 +2 are all zero, so the cosine of the angle between each pair is zero and the angle is 90°.