Hey Rajneesh,

You need to practice more. trigonometry is not a easy chapter. And also there is very less theory mainly there is formula so you don't need to study the theory. Just remember all the formula and practice a lot , make more than 300 question so you will get the benefite. You can practice in Amit M agrawal by Arihant publication.

or you can refer trigonometry 4th edition by mark dugopolski.