Two vectors ?⃗ and ? of the same length span a diamond, i.e. a parallelogram here all four sides are equal in length. Let ?1 and ?2 be the vectors defined by the diagonals of this diamond, as shown in...

Two vectors ?⃗ and ?   of the same length span a diamond, i.e. a parallelogram here all four sides are equal in length. Let ?1 and ?2 be the vectors defined by the diagonals of this diamond, as shown in the figure below.
Show, by calculating the scalar product ?1 ∘ ?2, that the diagonals of the diamond intersect each other at right angles.