Understand rotations and rotational symmetry. Grade 9 Alberta mathematics geometry.
Lesson 7.5 of Similarity & Transformations in Grade 9 Math — Alberta curriculum lessons.
A rotation happens when a shape is turned around a fixed point, called the center of rotation.The shape spins by a certain angle, but it does not change its size or shape — it just changes its orientation (the way it's facing).You can think of it like turning a wheel or spinning a logo — the shape stays the same, but it faces a new direction.
A shape has rotational symmetry if it can be turned (rotated) less than 360° and still look exactly the same as it did before turning.That means the shape matches itself at least once during the rotation before completing a full circle.
The order of rotational symmetry tells you how many times a shape matches itself in one full 360° turn.
For example:.
Each time the shape looks exactly the same, we count that as one "match."
If a shape has to be turned a full 360° before it matches itself again, it does not have rotational symmetry.
For example:.
A shape has rotational symmetry if it can be turned around its center and still look exactly the same before making a full 360° turn.The number of times a shape matches itself during this turn is called its Order of Rotational Symmetry.
The order tells us how many times a shape matches itself in one full 360° rotation.
For example:.
Take a rectangle (that's not a square).If you turn it around its center, it matches itself twice in one complete turn — once at 180° and again at 360°. This means the rectangle has rotational symmetry.
Create a free Studyio account to take the full lesson with voice-over teaching, practice questions and instant feedback.