It began in class with this problem. Find the dot product of 2 vectors: v1 a vector with components <4, 8> v2 a vector of length 1 angle pi/4 So, i have 2 ways of doing it. 1) v1.v2 = v1x.v2x + v1y.v2y 2) v1.v2 = |v1||v2|cos(theta) And they should come out the same but. 1) v1.v2 = 4cos(pi/4) + 8sin(pi/4) = 6√(2) 1) v1.v2 = √(42 + 82)cos(pi/4) = 2√(10) and 6√(2) ≠ 2√(10), so i wondered if i did something wrong. Then it tried different numbers and found out these two ways of computing the dot product of two vectors are never the same for an angle pi/4 except for vectors with components <a, 0> or <0, a> where a is any real number. I wonder if i computed anything wrong causing different results or is is that they are not the same?