Matrices and Vectors

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Pre-Calculus › Matrices and Vectors

Questions 1 - 10
1

Find the component form of the vector with

initial point

and

terminal point .

Explanation

To find the vector in component form given the initial and terminal points, simply subtract the initial point from the terminal point.

2

Find , then find its magnitude. and are both vectors.

Explanation

In vector addition, you simply add each component of the vectors to each other.

x component: .

y component: .

z component: .

The new vector is

.

To find the magnitude we use the formula,

Thus its magnitude is 5.

3

Find the dot product of the two vectors

and

.

Explanation

To find the dot product of two vectors,

find the product of the x-components,

find the product of the y-components,

and then find the sum.

4

Find the dot product of the two vectors

and

.

Explanation

To find the dot product of two vectors,

find the product of the x-components,

find the product of the y-components,

and then find the sum.

5

Find the parametric equations for a line parallel to and passing through the point (4, -3).

x = 4 - 7t

y = -3 + 3.5t

x = -7 + 4t

y = 3.5 - 3t

x = -3 + 3.5t

y = 4 - 7t

x = -3 - 3.5t

y = 4 + 7t

Explanation

A line through a point (x1,y1) that is parallel to the vector = (a1, a2) has the following parametric equations, where t is any real number.

Using the given vector and point, we get the following:

x = 4 - 7t

y = -3 + 3.5t

Each value of t creates a distinct (x, y) ordered pair. You can think of these points as representing positions of an object, and of t as representing time in seconds. Evaluating the parametric equations for a value of t gives us the coordinates of the position of the object after t seconds have passed.

6

Write a vector equation describing the line passing through P1 (1, 4) and parallel to the vector = (3, 4).

Explanation

First, draw the vector = (3, 4); this is represented in red below. Then, plot the point P1 (1, 4), and draw a line (represented in blue) through it that is parallel to the vector .

Screen shot 2020 05 29 at 11.28.09 am

We must find the equation of line . For any point P2 (x, y) on , . Since is on line and is parallel to , for some value of t. By substitution, we have . Therefore, the equation is a vector equation describing all of the points (x, y) on line parallel to through P1 (1, 4).

7

Find the parametric equations for a line parallel to and passing through the point (0, 5).

x = 5t

y = 3 + 2t

x = 3 + 2t

y = 5t

x = 3

y = 2 + 5t

x = 3t

y = 5 + 2t

Explanation

A line through a point (x1,y1) that is parallel to the vector = (a1, a2) has the following parametric equations, where t is any real number.

Using the given vector and point, we get the following:

x = 3t

y = 5 + 2t

Each value of t creates a distinct (x, y) ordered pair. You can think of these points as representing positions of an object, and of t as representing time in seconds. Evaluating the parametric equations for a value of t gives us the coordinates of the position of the object after t seconds have passed.

8

Write an equation in slope-intercept form of the line with the given parametric equations:

Explanation

Start by solving each parametric equation for t:

Next, write an equation involving the expressions for t; since both are equal to t, we can set them equal to one another:

Multiply both sides by the LCD, 6:

Get y by itself to represent this as an equation in slope-intercept (y = mx + b) form:

9

Write the parametric equation for the line y = -3x +1.5

x = -3t +1.5

y = -3t +1.5

x = t

y = 1.5t - 3

x = t

y = -3t +1.5

x = -3t +1.5

y = t

Explanation

In the equation y = -3x +1.5, x is the independent variable and y is the dependent variable. In a parametric equation, t is the independent variable, and x and y are both dependent variables.

Start by setting the independent variables x and t equal to one another, and then you can write two parametric equations in terms of t:

x = t

y = -3t +1.5

10

Find the parametric equations for a line parallel to and passing through the point (4, -3).

x = 4 - 7t

y = -3 + 3.5t

x = -7 + 4t

y = 3.5 - 3t

x = -3 + 3.5t

y = 4 - 7t

x = -3 - 3.5t

y = 4 + 7t

Explanation

A line through a point (x1,y1) that is parallel to the vector = (a1, a2) has the following parametric equations, where t is any real number.

Using the given vector and point, we get the following:

x = 4 - 7t

y = -3 + 3.5t

Each value of t creates a distinct (x, y) ordered pair. You can think of these points as representing positions of an object, and of t as representing time in seconds. Evaluating the parametric equations for a value of t gives us the coordinates of the position of the object after t seconds have passed.

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