# How do you calculate the derivative of #intcos(t)/t dt# from #[x,3]#?

##### 1 Answer

#### Answer:

Use the Fundamental Theorem of Calculus Part 1.

#### Explanation:

Fundamental Theorem of Calculus Part 1 says (in part) that if

This question asks about the function:

Clearly, in this question we have

Notice that FTC 1 requires the constant to be the lower limit of integration, so we use the properties of definite integral to write:

Now, we can see that

That's it. Stop! We are finished. Move on to the next question.

(On exams, the trickiest thing about this kind of question is often understanding how easy it is. We expect more work to be needed.)

**example**

Find the derivative of:

It is:

(It is so easy, that graders may penalize heavily for forgetting to change the variable