there are several ways to approach this

you can note that:

and

OR

you can do it the way you did, and you would get the same answer

OR

you can use the double angle formula:

........which, by the way, is how we know the first two formulas i gave you

and, by the way, it is NOT cos * 113.57, it is cos(113.57). the cosine function is an argument, you cannot treat it like a term unto itself and multiply it with something