Calculus 1 : Calculus

Study concepts, example questions & explanations for Calculus 1

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Example Questions

Example Question #1952 : Functions

A bar of length  is resting against a wall, the ground end  from the base of the wall. If the end resting on the ground is moved forward at a rate of , how fast does the end resting on the wall rise? The plane of the ground is perpendicular to the wall.

Possible Answers:

Correct answer:

Explanation:

The bar resting against the wall forms a right triangle, its length serving as the hypotenuse. This can be used to find the height of the end resting on the wall via the Pythagorean Theorem:

The rates of change can also be related using the Pythagorean Theorem:

Since the length of the bar isn't changing, 

Note that the negative value is used because the end on the ground is closing the distance to the wall.

Example Question #64 : How To Find Rate Of Change

A circle is stretching into an ellipse, its horizontal radius expanding at a rate of . If the circle has an area of , what is the rate of growth?

Possible Answers:

Correct answer:

Explanation:

The area of a circle is given by the formula:

This can be used to find the original radii:

Now, the area of an ellipse in terms of its vertical and horizontal radii is:

To relate rates of change, derive each side with respect to time:

Since the vertical radius does not change, let's designate it as ;

Example Question #61 : How To Find Rate Of Change

The shorter leg of a right triangle is growing at a rate of . If the shorter leg has a length of  and the hypotenuse has a length of , what is the rate of growth of the angle across from the shorter leg? The hypotenuse is growing, but the longer leg is not. 

Possible Answers:

Correct answer:

Explanation:

The hypotenuse and the shorter leg can be related in terms of the angle across from the leg:

This angle can be found as:

Now, rates of change can be related by deriving each side of the original equation with respect to time:

However, we do not know what  is. We can find this by using the Pythagorean theorem and once again deriving:

Since we're told the longer side does not change in length, , leaving

Now, let's return to this previous derivative using our known values and solve for :

Example Question #1955 : Functions

The circumference of a circle is increasing at a rate of . If the circle has an area of , what is the rate of growth of the area?

Possible Answers:

Correct answer:

Explanation:

Begin by finding the radius of the circle:

Now, rates of change can be related by taking the time derivative of both sides of an equation:

However, the rate of change of the radius, , is still unknown. It can be found by relating it to the circumference's rate of change:

Going back to our earlier equation, we can solve for the rate of change of the area:

Example Question #2981 : Calculus

The radius of a cylinder is given by the function , while the height at any time is given by the function . What is the rate of growth of the cylinder at time  ?

Possible Answers:

Correct answer:

Explanation:

The volume of a cylinder is given by the equation:

From this, the rate of change can be found by taking the derivative with respect to time:

It may be worth noting that at time  the cylinder actually begins to shrink.

Example Question #2982 : Calculus

If , what is ?

Possible Answers:

Correct answer:

Explanation:

The given function consists of a function, , inside another function, , such that .

Thus we can use the Chain Rule to find .

The Chain Rule says that if  

,

then 

.

Recall (or look up) that the derivative of sine is cosine, so , and use the Power Rule to get .

Combining the three functions , and , we have .

Note: The Power Rule says that for a function 

.

Example Question #2983 : Calculus

What is the rate of change of the function  when ?

Possible Answers:

Correct answer:

Explanation:

The rate of change of the function  at  is the value of the derivative 

 at .

Use the Power Rule to find that 

.

The rate of change at  is 

Note: The Power Rule says that for a function 

.

Example Question #2984 : Calculus

What is  if ?

Possible Answers:

Correct answer:

Explanation:

Since  is a quotient of two functions  and , we can use the Quotient Rule, which says that for a function

 and  by the Chain Rule.

Applying the Quotient Rule, 

.

Example Question #2985 : Calculus

What is the rate of change of  when ?

Possible Answers:

Correct answer:

Explanation:

We are looking for .

The Chain Rule says that for 

.

Applying the Chain Rule, 

.

So,

.

 

Example Question #71 : How To Find Rate Of Change

A spherical water balloon is filled at a rate of . What is the rate of change of the surface area of the water balloon when the balloon's radius is one meter?

Possible Answers:

Correct answer:

Explanation:

The rate of change of the surface area is found by relating the volume to the surface area:

We must solve for the rate of change of the radius using the volume equation, and then solve for the rate of change of the surface area by plugging in the given radius and rate of change of the radius:

 

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