Do I need to solve other books like RD Sharma if I am using Cengage?

Generally, if you are thoroughly completing the Cengage Maths series, you do not need to solve RD Sharma for JEE Main or Advanced.

• RD Sharma: This is an excellent book for building strong fundamentals and is highly recommended for school/board exams. It can be a good starting point if you feel your basics are very weak.
• Cengage: This series is specifically designed for the competitive level of JEE exams. The scope of theory and the difficulty of problems in Cengage are well beyond what is typically required from RD Sharma for JEE.

Actionable Thought: Focus on completing one primary resource like Cengage completely rather than doing multiple books partially. If you finish Cengage and still have time, your priority should be solving Previous Year Question (PYQ) books and taking mock tests, not another textbook like RD Sharma.