The points A, B and C have position vectors a=(2,1,2) b=(-3,2,5) and c=(4,5,-2) respectively, with respect to a fixed origin. The point D is such that ABCD, in >that order, is a parallelogram.
- Find the position vector of D
- Find the position vector of the point at which the diagonals of the >parallelogram intersect.
- Calculate the angle BAC, giving your answer to the nearest tenth of a degree.