210 likes | 532 Views
Rotational Symmetry. M6G1b – Investigate rotational symmetry, including degree of rotation. Vocabulary. 1) Rotate – to turn a figure around a fixed point. 2) Point of rotation - the point around which a figure is rotated (a.k.a. the center of rotation).
E N D
Rotational Symmetry M6G1b – Investigate rotational symmetry, including degree of rotation.
Vocabulary 1) Rotate – to turn a figure around a fixed point 2) Point of rotation - the point around which a figure is rotated (a.k.a. the center of rotation) 3) Rotational Symmetry – when a figure fits exactly on top of itself after a rotation of 180° or less 4) Angle of rotation – the smallest angle a figure can be rotated to look exactly the same
A square has rotational symmetry. • The smallest angle a figure can be rotated and still look the same is called the angle of rotation. • What is the angle of rotation of a square? 90°
Does a rectangle have rotational symmetry? What is the degree of rotation? 180°
Does each figure have rotational symmetry? 360 ÷ 4 = 90 360 ÷ 3 = 120 360 ÷ 6 = 60 To find the degree of rotation mathematically, divide ______ by the number of times the pattern _________ 360° repeats.
Do these figures have rotational symmetry? NO Yes - 90° Yes - 45° NO Yes - 180° Yes - 72°
Rotational Symmetry in the Alphabet Which letters have rotational symmetry? For those with rotational symmetry, what is the degree of rotation? A B C D E F G H I J 180° K L 180° M N 180° O P 180° Q R S T U V W X Y Z 180° 180° 180°
Rotational Symmetry all around us Which road signs have rotational symmetry?
Rotational Symmetry all around us 120° 180° 180°
Rotational Symmetry all around us 90° 120° 180°
Rotational Symmetry all around us 120° 180°