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Notes 1.4 Angle Measures

Notes 1.4 Angle Measures. LT – I can find and compare angle measures. Definition of an Angle. Angle – formed by two rays with the same endpoint . The rays are the sides or legs of the angle and the endpoint is the vertex. vertex. A. Naming an Angle.

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Notes 1.4 Angle Measures

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  1. Notes 1.4 Angle Measures LT – I can find and compare angle measures.

  2. Definition of an Angle Angle – formed by two rays with the same endpoint. The rays are the sides or legs of the angle and the endpoint is the vertex. vertex A. Naming an Angle The name can be the numberbetween the sides of the angle: /3. The name can be the vertexof the angle: /G. The name can be three points that include on each ray with the vertex written in the middle/AGCor / CGA.

  3. Example 1: Name the angle 4 ways. / 1 by NUMBER / ABC by POINTS with vertex in the middle / CBA / B by VERTEX point

  4. Example 2: Name the Adjacent Angles These angles are called “adjacent” which means “next to” because they share a ray. / POR & / ROQ or /O NOT / ORQ , / ORP,

  5. B. Classifying Angles Right = 90 Acute < 90 Straight = 180 Obtuse > 90

  6. State whether the following are acute, right, or obtuse. 1. 2. acute right 3. 4. ? acute obtuse ? 5. obtuse

  7. C. Angle Addition Postulate Example 1 Suppose that m/1 = 42 and m/ ABC= 88. Find m/2. 88° m/1 + m/2 = m/ ABC 42° 42 + m/2 = 88 m/2 = 46

  8. Example 2

  9. D. Congruent Angles Angles with the same measure are congruent. Congruent angles are marked by arcs. Example 1 Find m/GXF and m/IXJ 5x + 3 = 7x – 9 -5x -5x 3 = 2x – 9 +9 +9 12 = 2x 2 2 6 = x m/GXF = 5(6) + 3 = 33° m/IXJ = 7(6) – 9 = 33° 7x - 9 5x + 3

  10. When we use a protractor, we need to line it up correctly. You need to make sure the protractor is lined up correctly. Is this ready to measure the angle?

  11. Were you right......................it wasn’t Look for the upside down ‘T’ in the middle of the straight line on your protractor. This needs to be exactly on the vertex of your angle.

  12. We need to remember..... It doesn’t matter which way round the angle is, you ALWAYS need to line the upside down ‘T’ to the vertex of the angle.

  13. Now you are ready. Read from the 0°, and follow the inner set of numbers.

  14. Once you reach 30° you need to be careful!!! You then need to look at the 1° markings on the outer set of numbers.

  15. What does it measure? This angle measures 35°.

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