how do you use this grammar
是。。。的

比如我是有看法的
或者
当然我是做陈功的

not to sure what situations i should be using this. Is it used to express something very obvious? or something that should be clear?

Question

how do you use this grammar
是。。。的

比如  我是有看法的 
或者
 当然我是做陈功的

not to sure what situations i should be using this. Is it used to express something very obvious? or something that should be clear?

Answer

这  支  圆珠笔  新。
这  是  新的  圆珠笔。
这  支  圆珠笔  是  新的。

Answer

"是……的" is a common structure in modern Chinese. 
It's primarily used to highlight your point or make an emphasis. Pretty much like the "It is …… that" or "Someone does do something" structures in English.

这本书是她买的。
It is she who bought this book.

我是三年前学的游泳。
It was three years ago when I learned swimming.

我是有看法的。
I do have some thoughts (on this issue).

Answer

You need to read more Chinese and get a feel for when it's used.