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Using the midpoint formula

When the endpoints of a line segment are known, we can find the point midway between them. This point is known as the midpoint and the formula is known as the midpoint formula    . Given the endpoints of a line segment, ( x 1 , y 1 ) and ( x 2 , y 2 ) , the midpoint formula states how to find the coordinates of the midpoint M .

M = ( x 1 + x 2 2 , y 1 + y 2 2 )

A graphical view of a midpoint is shown in [link] . Notice that the line segments on either side of the midpoint are congruent.

This is a line graph on an x, y coordinate plane with the x and y axes ranging from 0 to 6. The points (x sub 1, y sub 1), (x sub 2, y sub 2), and (x sub 1 plus x sub 2 all over 2, y sub 1 plus y sub 2 all over 2) are plotted.  A straight line runs through these three points. Pairs of short parallel lines bisect the two sections of the line to note that they are equivalent.

Finding the midpoint of the line segment

Find the midpoint of the line segment with the endpoints ( 7 , −2 ) and ( 9 , 5 ) .

Use the formula to find the midpoint of the line segment.

( x 1 + x 2 2 , y 1 + y 2 2 ) = ( 7 + 9 2 , 2 + 5 2 ) = ( 8 , 3 2 )
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Find the midpoint of the line segment with endpoints ( −2 , −1 ) and ( −8 , 6 ) .

( 5 , 5 2 )

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Finding the center of a circle

The diameter of a circle has endpoints ( −1 , −4 ) and ( 5 , −4 ) . Find the center of the circle.

The center of a circle is the center, or midpoint, of its diameter. Thus, the midpoint formula will yield the center point.

( x 1 + x 2 2 , y 1 + y 2 2 ) ( 1 + 5 2 , 4 4 2 ) = ( 4 2 , 8 2 ) = ( 2 , −4 )
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Access these online resources for additional instruction and practice with the Cartesian coordinate system.

Key concepts

  • We can locate, or plot, points in the Cartesian coordinate system using ordered pairs, which are defined as displacement from the x- axis and displacement from the y- axis. See [link] .
  • An equation can be graphed in the plane by creating a table of values and plotting points. See [link] .
  • Using a graphing calculator or a computer program makes graphing equations faster and more accurate. Equations usually have to be entered in the form y= _____. See [link] .
  • Finding the x- and y- intercepts can define the graph of a line. These are the points where the graph crosses the axes. See [link] .
  • The distance formula is derived from the Pythagorean Theorem and is used to find the length of a line segment. See [link] and [link] .
  • The midpoint formula provides a method of finding the coordinates of the midpoint dividing the sum of the x -coordinates and the sum of the y -coordinates of the endpoints by 2. See [link] and [link] .

Section exercises

Verbal

Is it possible for a point plotted in the Cartesian coordinate system to not lie in one of the four quadrants? Explain.

Answers may vary. Yes. It is possible for a point to be on the x -axis or on the y -axis and therefore is considered to NOT be in one of the quadrants.

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Describe the process for finding the x- intercept and the y -intercept of a graph algebraically.

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Describe in your own words what the y -intercept of a graph is.

The y -intercept is the point where the graph crosses the y -axis.

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When using the distance formula d = ( x 2 x 1 ) 2 + ( y 2 y 1 ) 2 , explain the correct order of operations that are to be performed to obtain the correct answer.

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Algebraic

For each of the following exercises, find the x -intercept and the y -intercept without graphing. Write the coordinates of each intercept.

y = −3 x + 6

The x- intercept is ( 2 , 0 ) and the y -intercept is ( 0 , 6 ) .

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3 x 2 y = 6

The x- intercept is ( 2 , 0 ) and the y -intercept is ( 0 , −3 ) .

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Questions & Answers

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Astronomy (from Ancient Greek ἀστρονομία (astronomía) 'science that studies the laws of the stars') is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution.
Rafael
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Rosemary
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Rosemary
No
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the big bang theory is a theory which states that all matter was compressed together in one place the matter got so unstable it exploded releasing All its contents in the form of hydrogen
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I want to be an astronomer. That's my dream
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Who named the the whole galaxy?
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solar Univers
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Folakemi Reply
no
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bigbang is the beginning of the universe
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but thats just a theory
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nothing will happen, don't worry brother.
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what does comet means
GANGAIN Reply
these are Rocky substances between mars and jupiter
GANGAIN
Comets are cosmic snowballs of frozen gases , rock and dust that orbit the sun. They are mostly found between the orbits of Venus and Mercury.
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hey can anyone guide me abt international astronomy olympiad
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how can we learn right and true ?
Govinda Reply
why the moon is always appear in an elliptical shape
Gatjuol Reply
Because when astroid hit the Earth then a piece of elliptical shape of the earth was separated which is now called moon.
Hemen
what's see level?
lidiya Reply
Did you mean eye sight or sea level
Minal
oh sorry it's sea level
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according to the theory of astronomers why the moon is always appear in an elliptical orbit?
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hi !!! I am new in astronomy.... I have so many questions in mind .... all of scientists of the word they just give opinion only. but they never think true or false ... i respect all of them... I believes whole universe depending on true ...থিউরি
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we're all stars and galaxies a part of sun. how can science prove thx with respect old ancient times picture or books..or anything with respect to present time .but we r a part of that universe
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another theory of universe except big ban
Albash Reply
how was universe born
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there many theory to born universe but what is the reality of big bang theory to born universe
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there are many theories regarding this it's on you believe any theory that you think is true ex. eternal inflation theory, oscillation model theory, multiple universe theory the big bang theory etc.
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Michele
from where on earth could u observe all the stars during the during the course of an year
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I think it couldn't possible on earth
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is that so. the question was in the end of this chapter
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in theory, you could see them all from the equator (though over the course of a year, not at pne time). stars are measured in "declination", which is how far N or S of the equator (90* to -90*). Polaris is the North star, and is ALMOST 90* (+89*). So it would just barely creep over the horizon.
Christopher
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Source:  OpenStax, Algebra and trigonometry. OpenStax CNX. Nov 14, 2016 Download for free at https://legacy.cnx.org/content/col11758/1.6
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