Let's start from the left side, and manipulate it to get the right side, which would prove the identity.
We know that:
i)
ii)
.
From the above fundamental identities, we can rewrite the left hand side as:
,
which is what we needed to show.
We know that:
i)
ii)
From the above fundamental identities, we can rewrite the left hand side as:
which is what we needed to show.