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How to Construct Right, Acute, Obtuse & Equilateral Triangles

A triangle is identified by the angle it contains, the length of the lines that make up the triangle or both. A Right triangle contains a 90 degree angle. This can be any of the three angles that make up the triangle. An Acute triangle has an angle that is greater than 0 degrees and less than 90 degrees. An Obtuse triangle is an triangle that contains an angle that is greater than 90 degrees and less than 180 degrees. A triangle is identified as an equilateral triangle when all three sides of the triangle are equal in length. Constructing triangles is very simple with the use of a protractor and/or a compass.

Things You'll Need

  • Paper
  • Pencil
  • Ruler
  • Protractor
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Instructions

  1. Right Triangle

    • 1

      Draw a faint, straight line on your paper using a ruler.

    • 2

      Select a point on the line to be the vertex, or corner point. Mark the point with a small dot.

    • 3

      Line your protractor up with the point you marked.

    • 4

      Locate the point that is 90 degrees of your first line on your protractor.

    • 5

      Mark where 90 degrees is and trace a line from the 90 degree mark out to the side to create the 90 degree angle.

    • 6

      Line the ruler up with the first line and trace over the line with a heavier stroke of your pencil.

    • 7

      Line the ruler up with the second line and trace over the line with a heavier stroke of your pencil.

    • 8

      Connect the ends of the two lines to form a triangle. Use the ruler to ensure a straight line.

    Acute Triangle

    • 9

      Draw a horizontal line on your paper.

    • 10

      Place the protractor on the line and select a point that is less than 90 degrees from the first line.

    • 11

      Mark the point on the paper and draw a line at the angle you have chosen. Use a ruler to ensure a straight line.

    • 12

      Draw a third line to connect the two lines, creating a triangle. Use a ruler to make the line straight.

    Obtuse Triangle

    • 13

      Draw a horizontal line with a ruler on the paper.

    • 14

      Select and mark a spot where the vertex should go.

    • 15

      Place the protractor at the spot you marked.

    • 16

      Select a point between 90 and 180 degrees to mark the spot for your second point.

    • 17

      Trace a line between the two points to create the triangle.

    • 18

      Erase any lines outside of the connected points.

    Equilateral Triangle

    • 19

      Draw a straight line lightly on the paper using a ruler.

    • 20

      Mark a point on the line for a vertex.

    • 21

      Line your protractor up and find 60 degrees to the first line.

    • 22

      Mark the point at 60 degrees and draw a light line with the ruler.

    • 23

      Line the protractor back up with the first line you drew. Find 60 degrees in the other direction of the point.

    • 24

      Mark the point at 60 degrees and draw a light line with the ruler.

    • 25

      Line your ruler up and trace over the lines with a thicker stroke. The triangle will form inside the points' intersection. Erase the faint lines that may extend past these points.

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