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Welcome to the forum.
You haven’t told us what the optimization variables are. Nor do we know anything about the presumed values or properties of the input data.
It is your responsibility to prove that the optimization problem is convex. Displaying a graphic without context from a paper or book is not the best way to constructively engage on this forum.
Dear forum members sorry for my question which is not clear but I didn’t take it from book or paper. I’m try to formulate and solve my problem “maximize the secrecy rate of the system by Joint UAV trajectory and power allocation. I know nothing about convex optimization I learned it by myself from different source so I’m no so clear how to solve the problem using convex optimization and CVX tool.
I will send some variables so you will assist me the way forward
We can’t help until we know what the optimization problem is. Please, first carefully read the link in my previous post.
If you want to learn convex optimization, you can study and solve exercises in Convex Optimization by Boyd and Vandenberghe The degree of difficulty in doing so may depend on your “mathematical maturity”.
As for your problem, if it is your own problem, not from a book or paper, and “The problem becomes convex and can be solved by CVX after transform”, then presumably, you know what the transformation is, and how to formulate the transformed problem in CVX. Else, why would you write that?