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Introduction to LinesA line is infinite and straight. If you look atthe picture above, is a line, is alsoa line and is a line. A line is identifiedwhen you name two points on the line anddraw a line over the letters. A line isa set of continuous points that extendindefinitely in either of its direction. Linesare also named with lowercase letters or asingle lower case letter. For instance, Icould name one of the lines above simply byindicating an e.
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LinesThere are SEVEN types of LINES: Line segment Ray Horizontal line Vertical line Parallel line Intersecting line Perpendicular line
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lines1.A line segment is a straight line segment whichis part of the straight line between twopoints. To identify a line segment, one can writeAB or . The points on each side of the linesegment are referred to as the end points.
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A ray is the part of the line which consists of thegiven point and the set of all points on one side ofthe end point. A is the end point and this raymeans that all points starting from A are included inin the ray. A ray can also be written like:
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A horizontal line is one the goes left-to-right, parallel to the x-axis of the coordinate plane. All points on the linewill have the same y-coordinate. In the figure above, drageither point and note that the line is horizontal when they both have the same y-coordinate. A horizontal line has a slope of zero. As you move to the right along the line, it does not rise or fall at all. As you drag the points above, you can see that when the line is horizontal, the points both have the same y-coordinate, and the slope is zero.
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In geometry, a vertical line is one which runs from upand down the page. Its cousin is the horizontal linewhich runs left to right horizontal line. across thepage. A vertical line is perpendicular to a horizontalline
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Parallel linesParallel lines remain the same distance apart over their entire length. No matter how far you extend them, they will never meet.
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Intersecting lines• If two lines in the same plane are not parallel, they will intersect at a common point. Those lines are intersecting lines.
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Perpendicula r lines• Perpendicular means "at right angles". A line meeting another at a right angle, or 90° is said to be perpendicular to it. In the figure above, the line AB is perpendicular to the line DF. If they met at some other angle we would say that AB meets DF obliquely. Move the point A around and create both situations. Move the mouse carefully to get AB exactly perpendicular to DF A F D B
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Two rays that share the same endpoint form an angle. The point where therays intersect is called the vertex of the angle. The two rays are called thesides of the angle.We can specify an angle by using a point on each ray and the vertex. Theangle below may be specified as angle ABC or as angle CBA; you may alsosee this written as ABC or as CBA.
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There are SIX types of ANGLES:Right angleObtuse angleAcute angleStraight angleReflex angleFull angle
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Right angle: An angle whose measure is 90 degrees.