Prove that:
(i)tan720∘−cos270∘−sin150∘cos120∘=14
(ii)sin780∘sin480∘+cos120∘sin150∘=12
(iii)sin780∘sin120∘+cos240∘sin390∘=12
(iv)sin600∘cos390∘+cos480∘sin150∘=−1
(v)tan250∘cot405∘+tan765∘cot675∘=0