Hello Vin, as promised, I have solved the question by decomposing the forces into their respective x- and y-component. You realise that it is so much lengthier than the initial solution. I leave it to you which method to choose, but I would suggest to use the initial method I proposed (i.e., connect the vectors after forming a parallelogram). Additionally, this method is a “mechanics” way of solving the problem, while the initial proposed solution is a more “mathematics” way of solving the problem. Hope this clarifies your doubt.

This is the first page of the new solution.