Precalculus : Matrices and Vectors

Study concepts, example questions & explanations for Precalculus

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Example Questions

Example Question #1 : Express A Vector In Component Form

Write this vector in component form: Vector 2

Possible Answers:

Correct answer:

Explanation:

In order to find the horizontal component, set up an equation involving cosine with 7 as the hypotenuse, since the side in the implied triangle that represents the horizontal component is adjacent to the 22-degree angle:

First, find the cosine of 22, then multiply by 7

To find the vertical component, set up an equation involving sine, since the side in the implied triangle that represents the vertical component is opposite the 22-degree angle:

First, find the sine of 22, then multiply by 7

We are almost done, but we need to make a small adjustment. The picture indicates that the vector points up and to the left, so the horizontal component, 6.49, should be negative:

Example Question #31 : Algebraic Vectors And Parametric Equations

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

Possible Answers:

Correct answer:

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).

Example Question #1 : Parametric Equations

True or false: A line through P1 (x1, y1) that is parallel to the vector  is defined by the set of points  such that  for some real number t. Therefore, .

Possible Answers:

False

True

Correct answer:

True

Explanation:

This is true. The independent variable  in this equation is called a parameter. 

Example Question #32 : Algebraic Vectors And Parametric Equations

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

Possible Answers:

x = 3t

y = 5 + 2t

x = 3

y = 2 + 5t

x = 5t

y = 3 + 2t

x = 3 + 2t

y = 5t

Correct answer:

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.

Example Question #41 : Algebraic Vectors And Parametric Equations

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

Possible Answers:

x = -3 + 3.5t

y = 4 - 7t

x = -7 + 4t

y = 3.5 - 3t

x = -3 - 3.5t

y = 4 + 7t

x = 4 - 7t

y = -3 + 3.5t

Correct answer:

x = 4 - 7t

y = -3 + 3.5t

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.

Example Question #3 : Parametric Equations

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

Possible Answers:

x = -3t +1.5

y = -3t +1.5

x = t

y = -3t +1.5

x = t

y = 1.5t - 3

x = -3t +1.5

y = t

Correct answer:

x = t

y = -3t +1.5

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

Example Question #1361 : Pre Calculus

Write the parametric equation for the line y = 5x - 3.

Possible Answers:

x = t

y = 5t - 3

x = t

y = t

x = 5t - 3

y = t

x = 5t - 3

y = 5t - 3

Correct answer:

x = t

y = 5t - 3

Explanation:

In the equation y = 5x - 3, 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 = 5t - 3

Example Question #4 : Parametric Equations

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

 

Possible Answers:

 

Correct answer:

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, 4:

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

Example Question #5 : Parametric Equations

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

Possible Answers:

Correct answer:

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:

Example Question #6 : Parametric Equations

A football punter kicks a ball with an initial velocity of 40 ft/s at an angle of 29o to the horizontal. After 0.5 seconds, how far has the ball travelled horizontally and vertically?

Possible Answers:

Correct answer:

Explanation:

To solve this problem, we need to know that the path of a projectile can be described with the following equations:

In these equations, t is time and g is the acceleration due to gravity.

First, you need to write the position of the ball as a pair of parametric equations that define the path of the ball at anytime, t, in seconds:

As you set up the equation for y, use the value g = -32.

Finally, find x and y when t = .05:

Use a calculator to solve, making sure you are in degree mode: 

This means that after 0.5 seconds, the ball has travelled 17.5 feet horizontally and 5.7 feet vertically. 

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