1, When approaching a new question, even though it was hard, we can firstly have some tries, try some terms that represented in the question.

2, We can simplify the function before we start doing substitute, if it can.

3. Try to remember some of the important trigonometric transformation, it might help when we have no clue.

The question told us that f(t) has removale point when t=1,2,3,4…. and the general function discontinuous. However, back to the definition of integrade, its general idea is about divide part of a function into infinitely pieces and add those all together by select a certain point on the width you choose; thinking of this, we can apply that idea into this question, which we can choose that certain point ti without endpoints defined. Therefore, we can say that it is integrable.