Precalculus : Geometric Vectors

Study concepts, example questions & explanations for Precalculus

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Example Questions

Example Question #171 : Matrices And Vectors

Subtract:  \displaystyle \left \langle3, 4 \right \rangle - \left \langle -4,-3\right \rangle

Possible Answers:

\displaystyle \left \langle -7,7\right \rangle

\displaystyle \left \langle 7,7\right \rangle

\displaystyle \left \langle 7,-7\right \rangle

\displaystyle \left \langle -1,1\right \rangle

\displaystyle \left \langle 1,-1\right \rangle

Correct answer:

\displaystyle \left \langle 7,7\right \rangle

Explanation:

Subtract the first value of the first vector, and the second value of the first vector with the second value of the second vector.

\displaystyle \left \langle3, 4 \right \rangle - \left \langle -4,-3\right \rangle = \left \langle 3-(-4),4-(-3)\right \rangle

Double negative signs are converted to a positive sign.

\displaystyle \left \langle 3-(-4),4-(-3)\right \rangle = \left \langle 7,7\right \rangle

Example Question #21 : Geometric Vectors

Simplify:  \displaystyle \left \langle 2,-3,4\right \rangle+\left \langle-3,-3 \right \rangle-\left \langle5 \right \rangle

Possible Answers:

\displaystyle \left \langle -1,0,-1\right \rangle

\displaystyle \left \langle -6,-6,4\right \rangle

\displaystyle \left \langle -1,-6,-1\right \rangle

\displaystyle \left \langle -8\right \rangle

Correct answer:

Explanation:

The dimensions of the vectors are not the same.  Placeholders cannot be added to a vector.  Therefore, the values of the vectors cannot be added.

The correct answer is:  

Example Question #21 : Geometric Vectors

Find the norm of the vector \displaystyle \vec{v}=[2,4,3].

Possible Answers:

\displaystyle \left | \vec{v}\right |= \sqrt{29}\approx 5.385

\displaystyle \left | \vec{v}\right |= \sqrt{9} = 3

\displaystyle \left | \vec{v}\right |= 2\sqrt{6}\approx 4.899

\displaystyle \left | \vec{v}\right |= 9

Correct answer:

\displaystyle \left | \vec{v}\right |= \sqrt{29}\approx 5.385

Explanation:

We find the norm of a vector by finding the sum of each element squared and then taking the square root.

\displaystyle \left | \vec{v} \right |= \sqrt{2^2+4^2+3^2}=\sqrt{29}.

 

Example Question #22 : Geometric Vectors

Find the norm of the vector \displaystyle \vec{r}=7\hat{i} +4 \hat{j}+5 \hat{k}.

Possible Answers:

\displaystyle \left | \vec{r} \ \right | = 3 \sqrt{10}

\displaystyle \left | \vec{r}\right | = 2 \sqrt{13}

\displaystyle \left | \vec{r}\right | = 4

\displaystyle \left | \vec{r}\right | = 16

Correct answer:

\displaystyle \left | \vec{r} \ \right | = 3 \sqrt{10}

Explanation:

We find the norm of a vector by finding the sum of each component squared and then taking the square root of that sum.

\displaystyle \left | \vec{r}\right | = \sqrt{ 7^2+4^2+5^2 } = \sqrt{ 90 } = 3 \sqrt{10}

Example Question #1593 : Pre Calculus

Find the norm of the vector: \displaystyle < 3,-12,5.6,2,-9>

Possible Answers:

\displaystyle 31.6

\displaystyle \sqrt{269.36}\approx 16.41

\displaystyle 269.36

\displaystyle \sqrt{184.36}\approx 13.58

\displaystyle \sqrt{31.6}\approx 5.62

Correct answer:

\displaystyle \sqrt{269.36}\approx 16.41

Explanation:

The norm of a vector is also known as the length of the vector. The norm is given by the formula: 

\displaystyle \sqrt{\sum_{i=1}^nv_i^2}=\left \| v\right \|.

Here, we have

\displaystyle \left \|v \right \|=\sqrt{3^2+(-12)^2+5.6^2+2^2+(-9)^2}=\sqrt{269.36},

the correct answer.

Example Question #23 : Geometric Vectors

Find the norm of vector \displaystyle \left \langle -2,2\right \rangle.

Possible Answers:

\displaystyle 4

\displaystyle 2

\displaystyle \frac{1}{4}

\displaystyle 0

\displaystyle 2\sqrt2

Correct answer:

\displaystyle 2\sqrt2

Explanation:

Write the formula to find the norm, or the length the vector.

\displaystyle \left \| v\right \|=\sqrt{a_{1}^2+b_{2}^2}

Substitute the known values of the vector and solve.

\displaystyle \left \| v\right \|=\sqrt{(-2)^2+2^2}= \sqrt{4+4}=\sqrt8=2\sqrt2

Example Question #26 : Geometric Vectors

Find the norm (magnitude) of the following vector:

\displaystyle \vec{b}=3i+5j-6k

Possible Answers:

\displaystyle -\sqrt{70}

\displaystyle \sqrt{72}

\displaystyle \sqrt{70}

\displaystyle 70

\displaystyle 36

Correct answer:

\displaystyle \sqrt{70}

Explanation:

Use the following equation to find the magnitude of a vector:

\displaystyle \left \| \vec{b}\right \|=\sqrt{i^2+j^2+k^2}

In this case we have:

\displaystyle \vec{b}=3i+5j-6k

So plug in our values:

\displaystyle \left \| \vec{b}\right \|=\sqrt{3^2+5^2+(-6)^2}=\sqrt{70}

So:

\displaystyle \left \| \vec{b} \right \|=\sqrt{70}

Example Question #24 : Geometric Vectors

Find the product of the vector \displaystyle \vec{r}= 11\hat{i}+7\hat{j} and the scalar \displaystyle a=4.

Possible Answers:

\displaystyle a\vec{r}=44 \hat{j}+28\vec{i}

\displaystyle a\vec{r}=44 \hat{i}+28\vec{j}

\displaystyle a\vec{r}=72

\displaystyle a\vec{r}=72 \hat{i}

Correct answer:

\displaystyle a\vec{r}=44 \hat{i}+28\vec{j}

Explanation:

When multiplying a vector by a scalar we multiply each component of the vector by the scalar and the result is a vector:

\displaystyle a \vec{r}= 4 \cdot (11 \hat{i} + 7 \hat{j}) = 44 \hat{i}+28 \hat{j}

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