# Calculus 1 : Graphing Functions

## Example Questions

### Example Question #12 : Other Points

Find

.

Limit does not exist.

Explanation:

To evaluate this limit, all we need to do is factor the numerator and then cancel out the factor that is in common using the following formula:

With a simple algebra trick, we will be able to easily plug in  for :

### Example Question #13 : Other Points

Find all points on the graph of   where the tangent line is horizontal.

The tangent line is never horizontal for this graph.

Explanation:

To solve this problem, we need the chain rule,  the derivative of the trigonometric function cosine, and the power rule.

First let's apply the chain rule, which states:

In this problem,  and .

To find  , we need the power rule which states:

To find , we need the derivative of cosine which states:

Plugging these equations into the chain rule we obtain:

To find all points where the tangent line is horizontal, we must first take the derivative of the function and then set it equal to zero:

Setting this equal to zero, we obtain:

Therefore, either    or

Recall that from the unit circle, cosine equals zero at   and sine equals zero at .

So, at every multiple of , either  or .

Therefore,   because at each multiple of   , either   or

### Example Question #14 : Other Points

Evaluate the limit:

The limit does not exist at this point.

Explanation:

To begin, we need L'Hopital's Rule for this problem which states that if you get  when you plug in the value into your function when evalutating the limit, you should take the derivative of both the numerator and the denominator and then try plugging in your value again.

Since this is the case, we will take the derivative of the numerator and denominator.

To take the derivative of the numerator, we need the differentiation formulas for the trigonometric functions cosine and sine.

So, the derivative of the numerator is

To find the derivative of the denominator, we again need the differentiation formula for cosine, as well as the chain rule.

In this problem,  and

So, plugging these into the chain rule, we obtain:

Now let's put these expressions back into the numerator and denominator and again try to plug in our limit value:

### Example Question #15 : Other Points

Evaluate the limit:

The limit does not exist.

Explanation:

To solve this problem, we need L'Hopital's Rule, the derivative of the natural logarithm, the chain rule, the power rule, and the derivative of a constant.

Notice that if we plug in our  value into the function, we obtain a value of  .

L'Hopital's Rule, which states that if you plug in your limit value and obtain , you should take the derivative of the numerator and denominator and try plugging in your limit value again.

So we will take the derivative of the numerator and denominator.

For the numerator, we need the chain rule,the derivative of the natural logarithm, the derivative of a constant, and the power rule, which state:

For the numerator,  and .

Applying the chain rule to this expression yields:

To find the derivative of the denominator, we need the power rule and the derivative of a constant.

So now we have:

### Example Question #16 : Other Points

Find the x-coordinate of the critical points of .

Explanation:

We need to differentiate term by term, applying the power rule,

This gives us

The x-coordinate of the critical points are the points where the derivative equals 0. To find those, we can use the quadratic formula:

### Example Question #17 : Other Points

Find the x value of the critical points of .

Explanation:

We need to differentiate term by term, applying the power rule,

This gives us

The critical points are the points where the derivative equals 0. To find those x values, we can use the quadratic formula:

### Example Question #18 : Other Points

Find the x values of the critical points of .

Explanation:

We need to differentiate term by term, applying the power rule,

This gives us

The critical points are the points where the derivative equals 0. To find those, we can use the quadratic formula:

### Example Question #19 : Other Points

Find the x values for critical points of .

Explanation:

We need to differentiate term by term, applying the power rule,

This gives us

The critical points are the points where the derivative equals 0. To find those, we can use the quadratic formula:

### Example Question #1 : How To Find Decreasing Intervals By Graphing Functions

Find the interval(s) where the following function is decreasing. Graph to double check your answer.

Never

Always

Explanation:

To find when a function is decreasing, you must first take the derivative, then set it equal to 0, and then find between which zero values the function is negative.

First, take the derivative:

Set equal to 0 and solve:

Now test values on all sides of these to find when the function is negative, and therefore decreasing. I will test the values of -6, 0, and 2.

Since the only value that is negative is when x=0, the interval is only decreasing on the interval that includes 0. Therefore, our answer is:

### Example Question #1 : How To Find Decreasing Intervals By Graphing Functions

Find the interval(s) where the following function is decreasing. Graph to double check your answer.

Always

Never

Explanation:

To find when a function is decreasing, you must first take the derivative, then set it equal to 0, and then find between which zero values the function is negative.

First, take the derivative:

Set equal to 0 and solve:

Now test values on all sides of these to find when the function is negative, and therefore decreasing. I will test the values of 0, 2, and 10.

Since the only value that is negative is when x=0, the interval is only decreasing on the interval that includes 2. Therefore, our answer is: