Measuring Angles

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# Measuring Angles - PowerPoint PPT Presentation

Measuring Angles. Angle – formed by two rays with the same endpoint . The rays are the sides of the angle. The endpoint is the vertex of the angle. Vocabulary. Acute angle – 0 &lt; x &lt; 90 Right angle – x = 90 Obtuse angle – 90 &lt; x &lt; 180 Straight angle – x = 180

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### Measuring Angles

Angle – formed by two rays with the same endpoint.

The rays are the sidesof the angle.

The endpoint is the vertexof the angle.

Vocabulary
• Acute angle – 0 <x < 90
• Right angle – x = 90
• Obtuse angle– 90 < x < 180
• Straight angle – x = 180
• Congruent angles– angles with the same measure
Vocabulary Continued …
• Vertical angles – two angles whose sides are opposite rays.
• Adjacent angles – two coplanar angles with a common side, a common vertex, and no common interior points.
• Complementary angles – two angles whose measures have a sum of 90.
• Supplementary angles – two angles whose measures have a sum of 180.
Postulate 1 – 7 Protractor Postulate
• Let ray OA and ray OB be opposite rays in a plane. Ray OA, ray OB and all the rays with endpoint O that can be drawn on one side of line AB can be paired with the real numbers from 0 to 180 so that
• a. Ray OA is paired with 0 and ray OB is paired with 180.
• b. If ray OC is paired with x and ray OD is paired with y, then m < COD = lx – yl.
Postulate 1-8Angle Addition Postulate
• If point B is in the interior of < AOC, then the

m <AOB + m < BOC = m < AOC

• If < AOC is a straight angle, then the m < AOB + m < BOC = 180.