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Workforce LibreTexts

1.1: Angles

  • Page ID
    2631
  • What’s the deal with angles anyway?

    Before we even get into trigonometry, we need to discuss angles. Don’t worry. Things are not going to get too crazy. I promise. Let’s go over the basics first.

    Degree. One-three-hundred-and-sixtieth of the circumference of a circle. It is also the unit by which we measure angles.

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    Figure 1. Degrees

    Angle. This is the space between two intersecting lines.

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    Figure 2. Angle

    Complementary angles. These are two angles whose sum equals 90 degrees.

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    Figure 3. Complementary angle

    Supplementary angles. These are two angles whose sum equals 180 degrees.

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    Figure 4. Supplementary angle

    Acute angle. An angle that is less than 90 degrees.

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    Figure 5. Acute angle

    Obtuse angle. An angle that is greater than 90 degrees.

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    Figure 6. Obtuse angle

    Similar angles. It is possible for triangles to each have different sized sides but share the same sized angles. These are called similar angles.

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    Figure 7. Similar angles

    Right angle. This is an angle that is 90 degrees.

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    Figure 8. Right angle

    There is a ton of information about angles that we don’t need to get into. Remember: Try not to overcomplicate things. Just focus on the basics and you’ll be fine.