Elementary proofs of some q-identities of Jackson and Andrews-Jain

We present elementary proofs of three q-identities of Jackson. They are Jackson's terminating q-analogue of Dixon's sum, Jackson's q-analogue of Clausen's formula, and a generalization of both of them. We also give an elementary proof of Jain's q-analogue of terminating Watson's summation formula, which is actually equivalent to Andrews's q-analogue of Watson's formula.