(i) Prove by vector method that the diameter of a circle will subtend a right angle at a point on its circumference.(ii) If $\overrightarrow {a},\overrightarrow {b}$ and $\overrightarrow {c}$ represent the position vectors of the points with co-ordinates $(2,-10,2),(3,1,2)$ and $(2,1,3)$ respectively,find the value of $\overrightarrow {a}\times (\overrightarrow {b}\times \overrightarrow {c})$.
