If ā + b̄ + c̄ = 0̄, |ā| = 3, |b̄| = 5, and |c̄| = 7, then the angle between ā and b̄ is:

If a = (0, -1, 2), b = (1, 0, -1) and c = (2, -1, 0), then which of the following is a unit vector parallel to a - b - c?

If a = 2î + 3ȷ and b = î - ȷ, then a - b is:

If vectors a and b are perpendicular with |a| = 5 and |b| = 12, then |a + b| is equal to: