Segment Length

Who likes mountaineering? I recall, as part of our induction into college we the newbies had to trek long distances including mountain climbing. In order to prevent us from fainting along the journey, this long journey was split into several stop distances which were called "mountaineering segments". This article will explore everything you should know about segment length.

Segment Length Segment Length

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Contents
Table of contents

    What Does Segment Length Mean?

    The distance between two points on a line segment is the segment length.

    It is a very concise definition. For short, segment length is all about "from one point to another". Recall the mountaineering segments, those were just parts of the total distance that we had to cover.

    Segment length, An illustration of line segments with a road path, StudySmarterAn illustration of line segments with a road path, StudySmarter Originals

    Meanwhile, one cannot understand segment length without taking into perspective points, because these are your focus on locating where the segment starts as well as where it stops.

    What is the length of a segment between two points?

    The length of a segment between two points is the distance between two points. One point serves as the starting point which is the location from which the measurement begins. Meanwhile, the other is the endpoint which is the location where the measurement stops. It is sometimes a name with a small letter or to letters in upper cases. For instance, if there are two points A and B, we can call the length segment existing between A and B, or c, or we may just call the line segment, AB.

    Segment Length, An image of a segment length, StudySmarterAn image of a segment length, StudySmarter Originals

    What are the coordinates that exist on the length of a segment between two points?

    Since we are dealing with points, we need to know their position on the cartesian plane. In other words, we should know the position of the starting and ending point on the x and y-axis. This position is referred to as the coordinates of the points of the length segment and they are written in the form (x1, y1) and (x2, y2).

    Here,

    x1 means the position of the starting point in the x-axis,

    y1 means the position of the starting point in the y-axis,

    x2 means the position of the ending point in the x-axis

    and

    y2 means the position of the ending point in the y-axis.

    The image below describes this clearly.

    Segment length, A graphical image of two points of a segment length with its coordinates, StudySmarterA graphical image of two points of a segment length with its coordinates, StudySmarter Originals

    Now we can see the length segment as not only a distance, but we now consider the points that determine this distance.

    You should now think of how to determine the length of segments when you know their starting and ending points.

    What is the Formula for Segment Length Between Two Coordinates?

    To find the segment length, we can create a right-angled triangle and hence use Pythagoras' theorem to solve for the distance:

    Segment length, An image which shows the use of Pythagoras Theorem to calculate the length of a segment from two points, StudySmarterAn image shows the use of Pythagoras Theorem to calculate the length of a segment from two points, StudySmarter Originals

    We can see that y is the vertical distance between points A and B. x is the horizontal distance between points A and B. Hence, we can complete a Pythagorean triangle by inserting the distance between points A and B as d.

    Using Pythagoras' theorem, we know:

    d2=y2+x2

    Since the distance between two points cannot be negative, we know:

    d=+y2+x2

    For points A=(x1, y1) and B=(x2, y2):

    y=y2-y1 and x=x2-x1

    Therefore:

    d=+(y2-y1)2+(x2-x1)2

    Note that since ∆y and ∆x are both squared, there is no need to take the absolute value of these numbers as squaring them turns them positive. Also, note that the square root does not cancel the fact that ∆y and ∆x are squared as the equation adds these terms and does not multiply them.

    Find the distance between the points A=(5, 0) and B=(3,7)

    Solution:

    Substituting the coordinates into the equation for segment length:

    d=+(7-0)2+(3-5)2

    d=+72+(-2)2

    d=+49+4

    d=+53

    d=7.28 (2d.p.)

    Unless specified, you may choose to leave your answer in exact or numerical form.

    Length of a segment with endpoints

    In some cases, you may be given only the endpoints and midpoints and you would need to determine the length of the whole segment.

    The midpoint is the point halfway through the distance between the starting and the ending point.

    When this occurs, the first step to follow is to find the starting point which was not given initially. So, for a starting point A(x1, y2), midpoint M (xm, ym) and endpoint B (x2, y2), the midpoint for x-axis is calculated as:

    xm=x1+x22

    and the midpoint for the y-axis is calculated as:

    ym=y1+y22

    However, our interest is in finding the starting point when only the endpoint and the midpoint are given. In this case, you just need to make in their respective cases x1 or y1 the subject of the formula. This means that the coordinate of the starting point in the x-axis, x1 is:

    x1=2xm-x2

    Solved as

    xm=x1+x22xm=x1+x222xm=x1+x2x1=2xm-x2

    and the coordinate of the starting point in the y-axis, y1 is:

    y1=2ym-y2

    Solved as

    ym=y1+y22ym=y1+y222ym=y1+y2y1=2ym-y2

    If Nonso is on a journey in which his path is linear and he has currently covered half of the distance. If his current coordinate is (4, -2) and his journey terminates at K (9, 5), find the segment length of the whole journey.

    Solution:

    From the information given, Nonso is currently at the midpoint of the total journey which is the segment length of the journey. Since K is where the journey ends that means we have our endpoint. With these, we can now find the coordinates of our starting point as

    x1=2xm-x2xm=4x2=9x1=2(4)-9x1=8-9x1=-1

    and

    y1=2ym-y2ym=-2y2=5y1=2(-2)-5y1=-4-5y1=-9

    This means that Nonso started his journey at the point (-1,-9).

    Now we know his starting point, we can calculate the length of the segment for the journey as:

    d=+(y2-y1)2+(x2-x1)2d=+(5-(-9))2+(9-(-1))2d=+(5+9)2+(9+1)2d=+142+102d=+196+100d=296d=17.2

    What is the length of a segment of a circle?

    A segment of a circle is bounded by an arc and a chord. The line segment of a circle can either be the diameter of a circle when the line passes through the center of the circle or a chord if the line passes any other place apart from the center of a circle.

    To calculate the length of the segment of a circle when it passes the center, multiply the given radius by 2. However, when it passes outside the center then the length of a segment of a circle is the length of the chord calculated as

    d=2r×sin(θ2)

    Where r is the radius and θ is the angle subtended by the sector that forms the segment.

    This formula was gotten from the image description below;

    Segment length, An image illustrating the derivation of the length of a segment of a circle, StudySmarterAn image illustrating the derivation of the length of a segment of a circle, StudySmarter Originals

    from the image using SOHCAHTOA we get

    sin(θ2)=d2rr×sin(θ2)=d2d=2r×sin(θ2)

    Find the length of the line segment of a circle with a radius of 10 cm which subtends 120° at the center.

    Solution:

    Segment Length, Example of line segment in a circle, StudySmarterExample of line segment in a circle, StudySmarter Originals

    The length of the line segment is

    d=2r×sin(θ2)d=2×10 cm×sin(120°2)d=2×10 cm×sin(60°)d=20 cm×0.866d=17.32 cm

    Segment Length - Key takeaways

    • A line segment is the distance between two coordinates.
    • It is calculated using Pythagoras' theorem.
    • The segment length can be calculated when the endpoint and midpoint are given.
    • The line segment of a circle is either the diameter or chord depending on if the line passes through the center of a circle.
    Frequently Asked Questions about Segment Length

    What is a segment length?

    It is the distance between two points on a straight line.

    Where is the equation for segment length derived from?

    It originates from Pythagoras' theorem.

    What is the a circle segment?

    It is the area within a circle bound by a chord.

    How to find length of segments? 

    Length of segments can be found by simply applying the distance formula when the endpoints are known.

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