The sine function is non-concave and non-convex, which is difficult to handle.

I would like to ask whether the sine function can adopt the first-order Taylor expansion, sin(x)=sin(xl)+cos(xl)(x-xl) with the xl is the feasible point in the l-th iteration.

Since the sine function rarely appears in optimization, I don’t know whether it’s reasonable to do so

I am a student who is new to optimization. I hope someone can put forward their valuable suggestions and ideas.