Calculus 2 : Calculus II

Study concepts, example questions & explanations for Calculus 2

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Example Questions

Example Question #47 : Solving Integrals By Substitution

Evaluate the following integral:

\(\displaystyle \int 2t\cos(\sec(e^{3t^2}))dt\)

Possible Answers:

\(\displaystyle -\frac{1}{3}e^{3t^2}+C\)

\(\displaystyle \frac{1}{3}\cos(\sec(e^{3t^2}))+C\)

\(\displaystyle \frac{1}{3}e^{3t^2}+C\)

\(\displaystyle e^{3t^2}+C\)

Correct answer:

\(\displaystyle \frac{1}{3}e^{3t^2}+C\)

Explanation:

To evaluate the integral, we can first use the fact that cosine and secant are inverses of each other, so they cancel:

\(\displaystyle \int 2te^{3t^2}dt\)

Now, we must make the following substitution:

\(\displaystyle u=3t^2, du=6tdt\)

Rewriting the integral in terms of u and integrating, we get

\(\displaystyle \frac{1}{3}\int e^udu=\frac{1}{3}e^u+C\)

We used the following rule to integrate:

\(\displaystyle \int e^xdx=e^x+C\)

Finally, replace u with our original x term:

\(\displaystyle \frac{1}{3}e^{3t^2}+C\)

Example Question #48 : Solving Integrals By Substitution

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

Possible Answers:

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

\(\displaystyle \frac{3}{2}(x-2)^{\frac{4}{3}}+C\)

\(\displaystyle \frac{3}{2}(x^2-2)^{\frac{4}{3}}+C\)

\(\displaystyle \frac{3}{2}(u^2)^{\frac{4}{3}}+C\)

\(\displaystyle \frac{5}{2}(x^2-2)^{\frac{4}{3}}+C\)

Correct answer:

\(\displaystyle \frac{3}{2}(x^2-2)^{\frac{4}{3}}+C\)

Explanation:

To integrate this problem, you have to use "u" substitution. Assign \(\displaystyle x^2-2=u\). Then, find du, which is 2x. That works out since we can then replace the other x in the original problem. We will have to offset the 2 though: \(\displaystyle du=2x; \frac{1}{2}du=x\). Now plug in all the parts: \(\displaystyle \frac{1}{2}\int u^{\frac{1}{3}}du\). Now, integrate as normal, remembering to raise the exponent by 1 and then also putting that result on the bottom: \(\displaystyle \frac{1}{2}(\frac{3}{4})(u^{\frac{4}{3}})\). Simplify, add a C because it is an indefinite integral, and substitute your original expression back in: \(\displaystyle \frac{3}{2}(x^2-2)^{\frac{4}{3}}+C\).

Example Question #49 : Solving Integrals By Substitution

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

Possible Answers:

\(\displaystyle \frac{1}{3}ln\left | x^3-1 \right |\)

\(\displaystyle \frac{1}{3}ln\left | x^2-1 \right |+C\)

\(\displaystyle 3ln\left | x^3-1 \right |+C\)

\(\displaystyle ln\left | x^3-1 \right |+C\)

\(\displaystyle \frac{1}{3}ln\left | x^3-1 \right |+C\)

Correct answer:

\(\displaystyle \frac{1}{3}ln\left | x^3-1 \right |+C\)

Explanation:

To integrate this problem, use "u" substitution. Assign \(\displaystyle u=x^3-1\), \(\displaystyle du=3x^2; \frac{1}{3}du=x^2\). Substitute everything in so you can integrate: \(\displaystyle \frac{1}{3}\int \frac{1}{u}du\). Recall that when there is a single variable on the denominator, the integral is ln of that term. Therefore, after integrating, you get \(\displaystyle \frac{1}{3}ln\left | u \right |\). Sub back in your original expression and add C because it is an indefinite integral: \(\displaystyle \frac{1}{3}ln\left | x^3-1 \right |+C\).

Example Question #50 : Solving Integrals By Substitution

Evaluate the following integral using the substitution method:

\(\displaystyle \int^1_0 x^2(x^3+4)^3dx\)

Possible Answers:

\(\displaystyle \frac{5}{4}\)

\(\displaystyle \frac{1}{12}\)

\(\displaystyle \frac{123}{4}\)

\(\displaystyle \frac{61}{9}\)

\(\displaystyle \frac{1031}{24}\)

Correct answer:

\(\displaystyle \frac{123}{4}\)

Explanation:

\(\displaystyle \int^1_0 x^2(x^3+4)^3dx\)

Make the substitution:

\(\displaystyle u=x^3+4\)

\(\displaystyle du=3x^2dx\)

\(\displaystyle \frac{du}{3}=x^2dx\)

\(\displaystyle \int^1_0 \frac{u^3}{3}du=\frac{1}{12}u^4\left.\begin{matrix} \\ \end{matrix}\right|^1_0=\frac{1}{12}(x^3+4)^4 \left.\begin{matrix} \\ \end{matrix}\right|^1_0=\frac{123}{4}\)

Example Question #981 : Integrals

Solve: \(\displaystyle \int10e^{10x}\).

Possible Answers:

\(\displaystyle 10e^x + C\)

\(\displaystyle e^{10x}+C\)

\(\displaystyle 10\)

\(\displaystyle \frac{e^x}{10} + C\)

\(\displaystyle e^x + C\)

Correct answer:

\(\displaystyle e^{10x}+C\)

Explanation:

Substitute \(\displaystyle u=10x, du = 10 dx\):

\(\displaystyle \int e^{u}du\)

which is equal to

\(\displaystyle e^{u}+ C\).

Replace u with 10x:

\(\displaystyle e^{10x}+C\).

Example Question #982 : Integrals

\(\displaystyle \int cos^3xsinxdx\)

Possible Answers:

\(\displaystyle \frac{cos^2x}{2} +C\)

\(\displaystyle \frac{sin^4x}{4}\)

\(\displaystyle \frac{-cos^4x}{4} + C\)

\(\displaystyle cos^4x+C\)

\(\displaystyle \frac{cos^4x}{4} + C\)

Correct answer:

\(\displaystyle \frac{-cos^4x}{4} + C\)

Explanation:

Substitute \(\displaystyle u=cosx, du=-sinxdx\):

\(\displaystyle \int- u^3du=-\frac{u^4}{4} + C\).

Replace \(\displaystyle u=cos x\):

\(\displaystyle \frac{-cos^4x}{4} + C\).

 

Example Question #983 : Integrals

Solve \(\displaystyle \int sin^3x cos x dx\).

Possible Answers:

\(\displaystyle \frac{sin^2x}{2} +C\)

\(\displaystyle 3sin^2x +C\)

\(\displaystyle sin^4x +C\)

\(\displaystyle cos^4x+C\)

\(\displaystyle \frac{sin^4x}{4} +C\)

Correct answer:

\(\displaystyle \frac{sin^4x}{4} +C\)

Explanation:

Substitute \(\displaystyle u=sin x, du=cosx\):

\(\displaystyle \int u^3 du=\frac{u^4}{4} +C\).

Replace \(\displaystyle u=sin x\):

\(\displaystyle \frac{sin^4x}{4} +C\).

Example Question #984 : Integrals

Solve \(\displaystyle \int 5e^{5x}dx\).

Possible Answers:

\(\displaystyle e^{4x}+C\)

\(\displaystyle \frac{e^{6x}}{6} + C\)

\(\displaystyle e^{5x} + C\)

\(\displaystyle 5e^{x} + C\)

\(\displaystyle 5e^{4x} +C\)

Correct answer:

\(\displaystyle e^{5x} + C\)

Explanation:

Substitue \(\displaystyle u=5x, du=5\).

\(\displaystyle \int e^udu=e^u+C\).

Replace \(\displaystyle u=5x\):

\(\displaystyle e^{5x} + C\).

Example Question #985 : Integrals

Find \(\displaystyle \int \frac{dx}{(x+2)^4}\).

Possible Answers:

\(\displaystyle \frac{-(x+2)^{-5}}{5}+C\)

\(\displaystyle ln((x+2)^4)+C\)

\(\displaystyle \frac{-(x+2)^{-3}}{3}+C\)

\(\displaystyle {(x+2)^{-4}}+C\)

\(\displaystyle 4ln(x+2)+C\)

Correct answer:

\(\displaystyle \frac{-(x+2)^{-3}}{3}+C\)

Explanation:

Substitute \(\displaystyle u=x+2, du=dx\):

\(\displaystyle \int \frac{1}{u^4}du=-\frac{u^{-3}}{3}\).

Replace \(\displaystyle u=x+2\):

\(\displaystyle \frac{-(x+2)^{-3}}{3}+C\)

Example Question #986 : Integrals

Solve \(\displaystyle \int \frac{x^2}{x^3+1}\).

Possible Answers:

\(\displaystyle ln\left | x+1\right | + C\)

\(\displaystyle \frac{1}{3}ln\left | x^3+1\right | + C\)

\(\displaystyle 1\)

\(\displaystyle ln\left | x^3+1\right | + C\)

\(\displaystyle \frac{x^4}{4}+\frac{x^3}{3}+C\)

Correct answer:

\(\displaystyle \frac{1}{3}ln\left | x^3+1\right | + C\)

Explanation:

Substitute \(\displaystyle u=x^3 + 1, du=3x^2 dx\).

\(\displaystyle \int \frac{1}{3}u^{-1}du=\frac{1}{3}ln\left | u \right |+C\).

Replace \(\displaystyle u=x^3+1\):

\(\displaystyle \frac{1}{3}ln\left | x^3+1\right | + C\).

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