Prove that for any two subspaces W1 and W2 of an inner product space V, we have
a) (W1 + W2)^⊥ = W1^⊥ ∩ W2^⊥ and
b) (W1 ∩ W2)^⊥ = W1^⊥ + W2^⊥
Hint: The second follows from the first- you may use the fact that (W^⊥)^⊥ = W.
Any help would be greatly appreciated!