# Calculus 1 : How to find integral expressions

## Example Questions

### Example Question #61 : Equations

Evaluate the following indefinitie integral:

Explanation:

To evaluate the integral, use the inverse power rule.

This tells us that for each term we increase the power of x by 1 and divide by that same number. Don't forget to add a "plus C" to account for missing constants.

Applying that rule to this problem gives us the following for the first term:

And the following for the second term:

We can combine these terms and add our "C" to get the final answer:

### Example Question #62 : Equations

Evaluate the following indefinite integral:

Explanation:

To evaluate the integral, use the inverse power rule.

This tells us that for each term we increase the power of x by 1 and divide by that same number. Don't forget to add a "plus C" to account for missing constants.

Applying that rule to this problem gives us the following for the first term:

And the following for the second term:

We can combine these terms and add out "C" to get the final answer:

### Example Question #63 : Equations

Evaluate the following indefinite integral:

Explanation:

To evaluate the integral, use the inverse power rule.

This tells us that for each term we increase the power of x by 1 and divide by that same number. Don't forget to add a "plus C" to account for missing constants.

Applying that rule to this problem gives us the following for the first term:

And the following for the second term:

We can combine these terms and add our "C" to get the final answer:

### Example Question #64 : Equations

Which of the following integrals expresses the population of a square city with side lengths of  and population density given by  where  is distance from the north boundary of the city?

Explanation:

Here we want to integrate slices of the city with approximately uniform density. From the north side, we can divide the city into rectangles of length  and width . Each rectangle has a population density of approximately , where  is the distance from the north side of the  rectangle. Thus, the area of each rectangle is  and the total population of the rectangle is approximately  people. We sum up all of the rectangles on the interval  and take the limit as the number of rectangles on the interval approaches infinity. This limit takes the width of each rectangle and makes it infinitely small, making the density not just approximately uniform, but approaching perfectly uniform. This limit of a sum is one definition of the definite integral.

where  and .

### Example Question #65 : Equations

Find the indefinite integral

.

None of these

Explanation:

An integral is the opposite of a derivative. For the general integration rules for this problem we need to know that the integral of  is .

The integral of sine is negative cosine and the integral of  is itself. We must also use the chain rule for sin and for the exponential function which states that the derivative of   is .

The integral of  is

.

The integral of  is . The integral of  is.

We must also add a C as the integral is indefinite.

The final answer is

.

### Example Question #61 : Integral Expressions

Find the indefinite integral.

None of these

Explanation:

An integral is the opposite of a derivative. The rule for integrating  is .

This is enough information to find the integral of this function.

The integral can be found to be

The C is the constant of integration for indefinite integrals.

### Example Question #67 : Equations

Find the definite integral.

None of these

Explanation:

An integral is the opposite of a derivative. The integration rules needed for this problem are as follows.

The integral of  is  and the integral of cosine is sine.

This makes the integral

.

We must calculate this integral at the upper limit and subtract its value at the lower limit.

At the upper limit of  we can calculate

At the lower limit of 0

so the final answer is

.

### Example Question #68 : Equations

Find the average value of the function

on the interval

Keep your answer in the form of a fraction. (An exact answer)

Explanation:

Our bounds are given as [1,3]. Recall the power rule for integration:

For an average value, find the integral then divide it by your upper bound minus your lower bound.

You get,

Evaluate this expression from  to . That is, plug your upper bound into the expression for the variable ( in this case). Then subtracted the value you obtain from plugging in the lower bound for  from the value you got when plugging in the upper bound.

### Example Question #62 : Integral Expressions

Solve the definite integral.

None of these

Explanation:

To solve a definite integral you must first find the equation for the integral. Then you must plug in the upper limit and the lower limit and subtract the two values.

The integral of  is .

The integral expression equals

.

Plugging in 5 gets

.

Plugging in 1 gets

.

Finally the difference gives

.

### Example Question #63 : Integral Expressions

Find the indefinite integral.

None of these

Explanation:

For this problem we must use the strategy of integration by parts. It states that

.

For this problem we set

and .

The derivative of  is  and the integral of cos is sin.

Thus

and

The answer is then

.

The integral of sin is -cos so the final answer is

.

C is the constant of integration and we must add it to all indefinite integrals.