AP Calculus AB : AP Calculus AB

Study concepts, example questions & explanations for AP Calculus AB

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Example Questions

Example Question #98 : Comparing Relative Magnitudes Of Functions And Their Rates Of Change

Evaluate the following indefinite integral:

Possible Answers:

Correct answer:

Explanation:

Use substitution, where  and .  Thus, the integral can be rewritten as:

.

Substitution of  back into this expression gives the final answer:

Note that since this is an indefinite integral, the addition of a constant term (C) is required.

Example Question #132 : Functions, Graphs, And Limits

Evaluate the limit:

 

Possible Answers:

The limit does not exist

Correct answer:

Explanation:

When evaluating the limit as x approaches infinity, we must compare the magnitude of the functions. The exponential function in the numerator grows faster than the polynomial function (and any polynomial, for that matter) in the denominator, so the numerator dominates and the limit equals 

Example Question #1 : Applications Of Antidifferentiation

Find (dy/dx). 

sin(xy) = x + cos(y)

Possible Answers:

dy/dx = (1 – ycos(xy))/(xcos(xy) + sin(y))

dy/dx = (1 – cos(xy))/(cos(xy) + sin(y))

None of the above

dy/dx = (cos(xy) + sin(y))/(1 – cos(xy))

dy/dx = (xcos(xy) + sin(y))/(1 – ycos(xy)) 

Correct answer:

dy/dx = (1 – ycos(xy))/(xcos(xy) + sin(y))

Explanation:

The first step of the problem is to differentiate with respect to (dy/dx):

cos(xy)[(x)(dy/dx) + y(1)] = 1 – sin(y)(dy/dx)

*Note: When differentiating cos(xy) remember to use the product rule. (xy' + x'y)

Step 2: Clean the differentiated problem up 

cos(xy)(x)(dy/dx) + cos(xy)y = 1 – sin(y)(dy/dx)

cos(xy)(x)(dy/dx) + sin(y)(dy/dx) = 1 – cos(xy)y

Step 3: Solve for (dy/dx)

dy/dx = (1 – ycos(xy))/(xcos(xy) + sin(y))

 

Example Question #2 : Applications Of Antidifferentiation

Find the equation of the normal line at  on the graph y=x^{3}-6x+4.

Possible Answers:

y=\frac{-1}{6}x+\frac{1}{3}

y'=3x^{2}-6

y=\frac{-1}{6}x+2

Correct answer:

y=\frac{-1}{6}x+\frac{1}{3}

Explanation:

The answer is y=\frac{-1}{6}x+\frac{1}{3}.

 

y=x^{3}-6x+4

y'=3x^{2}-6   

Now plug in .

y'=3(2)^{2}-6 = 6  now we know 6 is the slope for the tangent line. However, we aren't looking for the slope of the tangent line. The slope of the normal line is the negative reciprocal of the tangent's slope; meaning the slope of the normal is \frac{-1}{6}. Now find the equation of the normal line.

y-0=\frac{-1}{6}(x-2)

y=\frac{-1}{6}x+\frac{1}{3}

Example Question #2 : Applications Of Antidifferentiation

f(x) = \frac{x^3}{1-x^2}

What is the derivative of

Possible Answers:

\frac{x^2(3-5x^2)}{1-x^2}

\frac{-2x^4-3 x^2(1-x^2)}{(1-x^2)^2}

\frac{x^2(3-x^2)}{(1-x^2)^2}

-x

Correct answer:

\frac{x^2(3-x^2)}{(1-x^2)^2}

Explanation:

Use the quotient rule. 

Example Question #4 : Applications Of Antidifferentiation

Find  if

 y=\frac{ln(x)}{x^{3}}

Possible Answers:

\frac{1}{x^{4}}

\frac{3}{x^{3}}

\frac{1+3ln(x)}{x^{4}}

\frac{ln(x)-1}{x^{4}}

y'=\frac{1-3ln(x)}{x^{4}}

Correct answer:

y'=\frac{1-3ln(x)}{x^{4}}

Explanation:

The answer is

 y'=\frac{1-3ln(x)}{x^{4}}

 

y=\frac{ln(x)}{x^{3}}

y'=\frac{(\frac{1}{x})x^{3}-ln(x)(3x^{3})}{x^{6}}

y'=\frac{x^{2}(1-3ln(x))}{x^{6}}

y'=\frac{1-3ln(x)}{x^{4}}

Example Question #3 : Applications Of Antidifferentiation

Find the derivative: 

Possible Answers:

Correct answer:

Explanation:

To find the derivative, multiply the exponent by the coefficent in front of the x term and then decrease the exponent by 1:

 

Example Question #6 : Solving Separable Differential Equations And Using Them In Modeling

Find the solution to the equation y'=y at x=2 with initial condition y(0)=2.

Possible Answers:

2e^2

1

e

2e

e^2

Correct answer:

2e^2

Explanation:

First, we need to solve the differential equation of y'=y.

, where is a constant

, where is a constant

To find , use the initial condition, , and solve:

Therefore, y=2e^x.

Finally, at , y(2)=2e^2.

Example Question #7 : Solving Separable Differential Equations And Using Them In Modeling

Solve the differential equation: 

Note that  is on the curve. 

Possible Answers:

Correct answer:

Explanation:

In order to solve differential equations, you must separate the variables first. 

Since point  is on the curve, .

To get rid of the log, raise every term to the power of e:

Example Question #6 : Applications Of Antidifferentiation

Suppose $1000 is invested in an account that pays 4.3% interest compounded continuously. Find an expression for the amount in the account after time .

Possible Answers:

y(t)=1000e^{0.043t}

y(t)=1000e^{t}

y(t)=4.3e^{1000t}

y(t)=4.3e^{t}

y(t)=43e^{1000t}

Correct answer:

y(t)=1000e^{0.043t}

Explanation:

The differential equation is \frac{dy}{dt}=0.043y, with boundary condition y(0)=1000.

 

This is a separable first order differential equation.

\frac{1}{y}dy=0.043dt

Integrate both sides.

ln(y)=0.043t+c

y=Ce^{0.043t}

Plug in the initial condition above to see that .

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