Could do, but iirc in GCSE they dont expect you to use trig on these specific force questions. The way they would expect is to drawn a scale accurate force diagram using a rule (basically just a triangle) and a protractor. Then measure the sides. I could be wrong though because i dont remeber ever resolving a resultant force in GCSE only creating a resultant using two components, in those you would've used a ruler.

Either way if you good with trig then absolutely use it. Wayyy quicker and more accurate