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2.1 Naming and Measuring Angles

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- An angle is formed by two rays or sides with a common endpoint called the vertex. Angles can be named using the vertex and endpoints, just the vertex if unique, or a number. - Angles are classified as acute (<90¡ã), right (90¡ã), or obtuse (>90¡ã and <180¡ã). A straight angle is 180¡ã. - Congruent angles have the same measure. Their measures can be indicated with arc marks or the lowercase "m" notation.

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Naming and Measuring Angles The student will be able to (I can): ? Correctly name an angle ? Classify angles as acute, right, or obtuse
angle ¨C a figure formed by two rays or sides with a common endpoint. Example: vertex ¨C the common endpoint of two rays or sides (plural: vertices). Example: A is the vertex of the above angle ¡ñ ¡ñ A C R
Notation: An angle is named one of three different ways: 1. By the vertex and a point on each ray (vertex must be in the middle) : ?TEA or ?AET 2. By its vertex (if only one angle): ?E 3. By a number: ?1 Methods 1 and 3 are always correct. Method 2 can only be used if there is only one angle at that vertex. ¡ñ ¡ñ ¡ñ E T A 1
Example Which name is not correct for the angle below? ?TRS ?SRT ?RST ?2 ?R ¡ñ ¡ñ ¡ñ S R T 2
Example Which name is not correct for the angle below? ?TRS ?SRT ?RST ?2 ?R ¡ñ ¡ñ ¡ñ S R T 2
acute angle ¨C an angle whose measure is greater than 0¡ã and less than 90¡ã. right angle ¨C an angle whose measure is exactly 90¡ã. obtuse angle ¨C an angle whose measure is greater than 90¡ã and less than 180¡ã.
straight angle ¨C an angle whose measure is exactly 180¡ã (also known as opposite rays, or a line) ¡ñ ¡ñ ¡ñ
congruent angles ¨C angles that have the same measure. m?WIN = m?LHS ?WIN ? ?LHS Notation: ¡°Arc marks¡± indicate congruent angles. Notation: To write the measure of an angle, put a lowercase ¡°m¡± in front of the angle bracket. ¡ñ ¡ñ ¡ñ ¡ñ ¡ñ ¡ñ L H S W I N m?WIN is read ¡°the measure of angle WIN¡±

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2.1 Naming and Measuring Angles

  • 1. Naming and Measuring Angles The student will be able to (I can): ? Correctly name an angle ? Classify angles as acute, right, or obtuse
  • 2. angle ¨C a figure formed by two rays or sides with a common endpoint. Example: vertex ¨C the common endpoint of two rays or sides (plural: vertices). Example: A is the vertex of the above angle ¡ñ ¡ñ A C R
  • 3. Notation: An angle is named one of three different ways: 1. By the vertex and a point on each ray (vertex must be in the middle) : ?TEA or ?AET 2. By its vertex (if only one angle): ?E 3. By a number: ?1 Methods 1 and 3 are always correct. Method 2 can only be used if there is only one angle at that vertex. ¡ñ ¡ñ ¡ñ E T A 1
  • 4. Example Which name is not correct for the angle below? ?TRS ?SRT ?RST ?2 ?R ¡ñ ¡ñ ¡ñ S R T 2
  • 5. Example Which name is not correct for the angle below? ?TRS ?SRT ?RST ?2 ?R ¡ñ ¡ñ ¡ñ S R T 2
  • 6. acute angle ¨C an angle whose measure is greater than 0¡ã and less than 90¡ã. right angle ¨C an angle whose measure is exactly 90¡ã. obtuse angle ¨C an angle whose measure is greater than 90¡ã and less than 180¡ã.
  • 7. straight angle ¨C an angle whose measure is exactly 180¡ã (also known as opposite rays, or a line) ¡ñ ¡ñ ¡ñ
  • 8. congruent angles ¨C angles that have the same measure. m?WIN = m?LHS ?WIN ? ?LHS Notation: ¡°Arc marks¡± indicate congruent angles. Notation: To write the measure of an angle, put a lowercase ¡°m¡± in front of the angle bracket. ¡ñ ¡ñ ¡ñ ¡ñ ¡ñ ¡ñ L H S W I N m?WIN is read ¡°the measure of angle WIN¡±