I'm puzzled by a problem about simplification of trigonometric functions.
I want to merge the terms with the same trig functions without changing other parts.
I tried 'Simplify' or 'TrigReduce', but 'TrigReduce' fails to merge the terms and 'Simplify' would do but it also simplifies the coefficients and the variables in trig functions.
For example, I want expr (1) to be rewritten as expr (2), how could I possibly write the code?
If I use 'Simplify', the result would be
both the coefficients of Sin[x] and variable of 2x+2y are simplified, which fails my request.
It's no more than a minor problem in simplification and won't affect much, but I really wish it be solved.
Thank you very much