Calculus 3 : Calculus 3

Study concepts, example questions & explanations for Calculus 3

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Example Questions

Example Question #73 : Dot Product

Given the following two vectors, \(\displaystyle \overrightarrow{a}=\begin{bmatrix} -7\\ -7\\5 \end{bmatrix}\) and \(\displaystyle \overrightarrow{b}=\begin{bmatrix} 7\\-5 \\5 \end{bmatrix}\), calculate the dot product between them,\(\displaystyle \overrightarrow{a}\cdot\overrightarrow{b}\).

Possible Answers:

\(\displaystyle -26\)

\(\displaystyle -14\)

\(\displaystyle 11\)

\(\displaystyle 13\)

\(\displaystyle 0\)

Correct answer:

\(\displaystyle 11\)

Explanation:

The dot product of a paired set of vectors can be found by summing up the individual products of the multiplications between matched directional vectors.

\(\displaystyle \overrightarrow{a}=\begin{bmatrix} a_1\\a_2 \\ ...\\ a_n \end{bmatrix}\)

\(\displaystyle \overrightarrow{b}=\begin{bmatrix}b_1 \\b_2 \\...\\b_n \end{bmatrix}\)

\(\displaystyle \overrightarrow{a}\cdot\overrightarrow{b}=a_1b_1+a_2b_2+a_3b_3+...+a_nb_n\)

Note that the dot product is a scalar value rather than a vector; there's no directional term.

Now considering our problem, we're given the vectors

\(\displaystyle \overrightarrow{a}=\begin{bmatrix} -7\\ -7\\5 \end{bmatrix}\) and \(\displaystyle \overrightarrow{b}=\begin{bmatrix} 7\\-5 \\5 \end{bmatrix}\)

The dot product can be found following the example above:

\(\displaystyle \overrightarrow{a}\cdot\overrightarrow{b}=-49+35+25=11\)

Example Question #74 : Dot Product

Given the following two vectors, \(\displaystyle \overrightarrow{a}=\begin{bmatrix} -3\\7 \\7 \end{bmatrix}\) and \(\displaystyle \overrightarrow{b}=\begin{bmatrix} -4\\2 \\1 \end{bmatrix}\), calculate the dot product between them,\(\displaystyle \overrightarrow{a}\cdot\overrightarrow{b}\).

Possible Answers:

\(\displaystyle 33\)

\(\displaystyle 15\)

\(\displaystyle 45\)

\(\displaystyle -11\)

\(\displaystyle 9\)

Correct answer:

\(\displaystyle 33\)

Explanation:

The dot product of a paired set of vectors can be found by summing up the individual products of the multiplications between matched directional vectors.

\(\displaystyle \overrightarrow{a}=\begin{bmatrix} a_1\\a_2 \\ ...\\ a_n \end{bmatrix}\)

\(\displaystyle \overrightarrow{b}=\begin{bmatrix}b_1 \\b_2 \\...\\b_n \end{bmatrix}\)

\(\displaystyle \overrightarrow{a}\cdot\overrightarrow{b}=a_1b_1+a_2b_2+a_3b_3+...+a_nb_n\)

Note that the dot product is a scalar value rather than a vector; there's no directional term.

Now considering our problem, we're given the vectors

\(\displaystyle \overrightarrow{a}=\begin{bmatrix} -3\\7 \\7 \end{bmatrix}\) and \(\displaystyle \overrightarrow{b}=\begin{bmatrix} -4\\2 \\1 \end{bmatrix}\)

The dot product can be found following the example above:

\(\displaystyle \overrightarrow{a}\cdot\overrightarrow{b}=12+14+7=33\)

Example Question #75 : Dot Product

Given the following two vectors, \(\displaystyle \overrightarrow{a}=\begin{bmatrix} -6\\8 \\3 \end{bmatrix}\) and \(\displaystyle \overrightarrow{b}=\begin{bmatrix}-6 \\-2 \\7 \end{bmatrix}\), calculate the dot product between them,\(\displaystyle \overrightarrow{a}\cdot\overrightarrow{b}\).

Possible Answers:

\(\displaystyle 41\)

\(\displaystyle 15\)

\(\displaystyle 56\)

\(\displaystyle -5\)

\(\displaystyle 61\)

Correct answer:

\(\displaystyle 41\)

Explanation:

The dot product of a paired set of vectors can be found by summing up the individual products of the multiplications between matched directional vectors.

\(\displaystyle \overrightarrow{a}=\begin{bmatrix} a_1\\a_2 \\ ...\\ a_n \end{bmatrix}\)

\(\displaystyle \overrightarrow{b}=\begin{bmatrix}b_1 \\b_2 \\...\\b_n \end{bmatrix}\)

\(\displaystyle \overrightarrow{a}\cdot\overrightarrow{b}=a_1b_1+a_2b_2+a_3b_3+...+a_nb_n\)

Note that the dot product is a scalar value rather than a vector; there's no directional term.

Now considering our problem, we're given the vectors

\(\displaystyle \overrightarrow{a}=\begin{bmatrix} -6\\8 \\3 \end{bmatrix}\) and \(\displaystyle \overrightarrow{b}=\begin{bmatrix}-6 \\-2 \\7 \end{bmatrix}\)

The dot product can be found following the example above:

\(\displaystyle \overrightarrow{a}\cdot\overrightarrow{b}=36-16+21=41\)

Example Question #76 : Dot Product

Given the following two vectors, \(\displaystyle \overrightarrow{a}=\begin{bmatrix} 4\\ -9\\-9 \end{bmatrix}\) and \(\displaystyle \overrightarrow{b}=\begin{bmatrix} -7\\ 7\\9 \end{bmatrix}\), calculate the dot product between them,\(\displaystyle \overrightarrow{a}\cdot\overrightarrow{b}\).

Possible Answers:

\(\displaystyle 108\)

\(\displaystyle 214\)

\(\displaystyle -126\)

\(\displaystyle -172\)

\(\displaystyle -144\)

Correct answer:

\(\displaystyle -172\)

Explanation:

The dot product of a paired set of vectors can be found by summing up the individual products of the multiplications between matched directional vectors.

\(\displaystyle \overrightarrow{a}=\begin{bmatrix} a_1\\a_2 \\ ...\\ a_n \end{bmatrix}\)

\(\displaystyle \overrightarrow{b}=\begin{bmatrix}b_1 \\b_2 \\...\\b_n \end{bmatrix}\)

\(\displaystyle \overrightarrow{a}\cdot\overrightarrow{b}=a_1b_1+a_2b_2+a_3b_3+...+a_nb_n\)

Note that the dot product is a scalar value rather than a vector; there's no directional term.

Now considering our problem, we're given the vectors

\(\displaystyle \overrightarrow{a}=\begin{bmatrix} 4\\ -9\\-9 \end{bmatrix}\) and \(\displaystyle \overrightarrow{b}=\begin{bmatrix} -7\\ 7\\9 \end{bmatrix}\)

The dot product can be found following the example above:

\(\displaystyle \overrightarrow{a}\cdot\overrightarrow{b}=-28-63-81=-172\)

Example Question #2391 : Calculus 3

Evaluate the dot product \(\displaystyle < t,2t,t^3> \cdot < \sin(t),\cos(t),\ln(t)>\).

Possible Answers:

\(\displaystyle < t\sin(t),2t\cos(t),t^3\ln(t)>\)

None of the other answers

\(\displaystyle < 0,0,0>\)

\(\displaystyle < t\cos(t),-2t\sin(t),t^2>\)

Correct answer:

None of the other answers

Explanation:

The correct answer is \(\displaystyle t\sin(t)+2t\cos(t)+t^3\ln(t)\).

 

To compute the dot product, we take the corresponding components of each vector, and multiply them together. In this case, we have \(\displaystyle (t)(\sin(t))+(2t)(\cos(t))+(t^3)(\ln(t))=t\sin(t)+2t\cos(t)+t^3\ln(t)\).

Note that taking the dot product of any two vectors will always return a scalar-valued expression (or just a simple scalar). There should be no vector brackets in your answer.

Example Question #2392 : Calculus 3

Find the dot product of the two vectors:

\(\displaystyle \mathbf{u}=\left [ \frac{2\sqrt{2}}{3}, 7, 4\sqrt{3}\right ], \mathbf{v}=\left [ 6\sqrt{2}, 0, \frac{5}{2} \right ]\)

Possible Answers:

22.14

19.07

20.72

23.58

25.32

Correct answer:

25.32

Explanation:

The dot product of two vectors is defined as:

\(\displaystyle \mathbf{u} \cdot\mathbf{v}=u_xv_x+u_yv_y+u_zv_z\)

For the given vectors, this is:

\(\displaystyle \mathbf{u} \cdot\mathbf{v}=(\frac{2\sqrt{2}}{ {3}})(6\sqrt{2})+(7)(0)+(4\sqrt{3})(\frac{5}{2})\)

\(\displaystyle \mathbf{u} \cdot\mathbf{v}=8+0+10\sqrt{3}=25.32\)

Example Question #2393 : Calculus 3

Find the magnitude of the following vector:

\(\displaystyle \mathbf{u}=6\mathbf{i}+3\mathbf{j}-4\mathbf{k}\)

Possible Answers:

\(\displaystyle \sqrt{5}\)

\(\displaystyle \sqrt{29}\)

\(\displaystyle \sqrt{13}\)

\(\displaystyle \sqrt{70}\)

\(\displaystyle \sqrt{61}\)

Correct answer:

\(\displaystyle \sqrt{61}\)

Explanation:

The magnitude of a vector is given by:

\(\displaystyle |\mathbf{u}|=\sqrt{u_x^2+u_y^2+u_z^2}=\sqrt{6^2+3^2+(-4)^2}=\sqrt{36+9+16}=\sqrt{61}\)

Example Question #81 : Dot Product

Find the dot product:  \(\displaystyle \left \langle -2,9\right \rangle\cdot \left \langle -3,7\right \rangle\)  

Possible Answers:

\(\displaystyle \left \langle -5,16\right \rangle\)

\(\displaystyle \left \langle 6,63\right \rangle\)

\(\displaystyle 10\)

\(\displaystyle 11\)

\(\displaystyle 69\)

Correct answer:

\(\displaystyle 69\)

Explanation:

Write the dot product formula.

\(\displaystyle a\cdot b = a_1b_1+a_2b_2\)

Substitute the values of the vectors and solve.  The dot product will result in a number, not a vector.

\(\displaystyle (-2)(-3) + (9)(7) = 6 +63 =69\)

The dot product is:  \(\displaystyle 69\)

Example Question #82 : Dot Product

Find the length \(\displaystyle \small ||v||\) of the vector \(\displaystyle \small v=(1,\sqrt{3})\)

Possible Answers:

\(\displaystyle \small \small \small ||v||=4\)

\(\displaystyle \small \small \small ||v||=\sqrt{1+\sqrt{3}}\)

\(\displaystyle \small \small ||v||=2\)

\(\displaystyle \small \small \small ||v||=1+\sqrt{3}\)

Correct answer:

\(\displaystyle \small \small ||v||=2\)

Explanation:

To find the length \(\displaystyle \small ||v||\) of the vector \(\displaystyle \small v=(1,\sqrt{3})\), we take the square root of the dot product \(\displaystyle \small v\cdot v\):

\(\displaystyle \small \small ||v||=\sqrt{v\cdot v}=\sqrt{1^2+\sqrt{3}^2}=\sqrt{4}=2\)

Example Question #83 : Dot Product

Find the length \(\displaystyle \small ||v||\) of the vector \(\displaystyle \small \small v=(15,12)\).

Possible Answers:

\(\displaystyle \small \small \small ||v||=27\)

\(\displaystyle \small \small \small ||v||=\sqrt{370}\)

\(\displaystyle \small \small \small ||v||=369\)

\(\displaystyle \small \small \small ||v||=\sqrt{369}\)

Correct answer:

\(\displaystyle \small \small \small ||v||=\sqrt{369}\)

Explanation:

To find the length \(\displaystyle \small ||v||\) of the vector \(\displaystyle \small \small v=(15,12)\), we take the square root of the dot product \(\displaystyle \small v\cdot v\):

\(\displaystyle \small \small \small ||v||=\sqrt{v\cdot v}=\sqrt{15^2+12^2}=\sqrt{225+144}=\sqrt{369}\)

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