Am an bio student so i …

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To understand the methods used Remember all the integration formulae described in class 11 th and 12 th physics ncert Understand and remember all the rules of integration. Understand integration as the summation ie summing up of differential elements dx *f(x) between particular values of x and x+dx such that dx is very small so the change in f(x) between x and x+dx is negligible. This is basic concept of integration on a graph . Whenever we derieve a new result we use this concept . So for example we know the result of a point charge then we can use the point charge as an element(largest entity whose result is known)while deriving the result of a ring considering the ring is made up of point charges and the result of the point charge can be expressed as a function of x f(x) or it depends on the values of x following particular rule or formula . So we are doing the same and adding the thin vertical lines below f(x) vs x graph areas as elements . Similarly while you derieve the result of disk ,you consider elements as rings such that you know the result of a ring. Also being a bio student you are usually told to remember the formulae without understanding the derivation .In that case just remember it as you know the result of a small part ,you want the result of whole entity ,so you add up the useful effects of individual entities that are effective to get net result which you name as integration and use formulae. If you would still like to spend some time to understand the then there are books which are based on maths required for physics. You may download the pdf of halliday resnick and walker physics from archive.org which describes the methods used for derivations using calculus between the chapters. For chemistry usually the derivation are simple and if you understand those used in physics then chemistry ones should be easy for you. You can go to your teachers after or in between classes to explain and understand them in detail.