First, a rather belated Welcom to Math Help Forum!
So, as I said in my previous post:(Do you understand how I got this? I used the Sine Rule on the lower triangle, having first used Pythagoras' Theorem on the upper triangle.)
So, noting that :Then I should leave the answer as:
, whereBut you could combine these into a single expression by substituting for each of the variables if you wish.
(or you could simply say .)