Transcript Document
Geometry Level 1 Angle names Acute angle Web animation An acute angle is between 0 and 90 degrees Angle names Obtuse angle Website animation An obtuse angle is between 90 and 180 degrees Angle names Reflex angle A reflex angle is between 180 and 360 degrees Angle names Right angle A right angle is 90 degrees Angle names Right angle A right angle is 90 degrees Angle names Straight angle A straight line is 180 degrees Naming angles • The angle is at B A B ABC C Guessing the angle size • The clock is divided into 12 hours. • One complete circle is 360 degrees. • Each hour makes 30 degrees. 30 60 90 120 210 270 180 What angle do the hands of the clock make? • 4 lots of 30 degrees. • 120 degrees. • OR the reflex angle is 240 degrees. Guess the angle size 150 210 60 300 OR 90 270 170 190 Complementary angles • Two angles which add up to 90 degrees are said to be complementary. Complementary angles • What is the complement of 58 degrees? ? Complementary angles • 32 degrees 58 32 90 Complementary angles • What is the complement of 45 degrees? ? ? Complementary angles • 45 degrees 45 45 90 Supplementary angles • Two angles which add up to 180 degrees are said to be supplementary. Supplementary angles • What is the supplement of 120 degrees? ? ? Supplementary angles • 60 degrees? ? Supplementary angles • What is the supplement of 40 degrees? ? Supplementary angles • What is the supplement of 140 degrees? Measuring angles • We use a protractor to measure angles. There are two scales marked on your protractor First decide if your angle is acute or obtuse This angle is acute Read the acute scale. The angle is 56 degrees. This angle is obtuse. Read the obtuse scale. The angle is 124 degrees.