Hi there, I was given this equation, cosh(A+B)=cos(A).cosh(B) + sinh(A).sinh(B) then I was told to write down the definition of cosh(A+B) which I did. But then i'm told to substitue the defintions of cosh(A), sinh(A), cosh(B) and sinh(B) into the right hand side of the equation, and to simplify....now I don't understand what it means by that? Is it doing the same way as the definition for cosh(A+B) (where you replace the e^t with A...and so on??) I'm not quite sure what it wants out of that one??