How to solve cyclic relationship in SQL?

I have table for students , instructors and courses.

1. Relationship between instructor and course many to many (as instructor can teach many course and course can be tough by many instructors ) I create instructorcourse table to break many to many
2. Relationship between student and course many to many (as student can register in many courses and course have many students) I create studentcourse table to break many to many
3. Relationship between student and instructor one to many So l have a problem in cyclic relationship