Rotations Flashcards

All 6 cards in this deck

What must you state to describe fully a rotation?

Rotation, the angle, the direction (clockwise or anticlockwise) and the centre of rotation.

True or false? A rotation of $180^\circ$ must have its direction stated to be fully described.

False. Clockwise and anticlockwise $180^\circ$ give the same image, so only the angle and centre are needed.

A rotation of $90^\circ$ anticlockwise about a point is the same as which other rotation about that point?

A rotation of $270^\circ$ clockwise.

What are the steps to rotate a shape about a given centre?

e.g. rotate $90^\circ$ clockwise about the origin

1. Trace the shape and mark the centre on the tracing paper.
2. Hold a pencil point on the centre and turn the paper $90^\circ$ clockwise.
3. Mark the new vertex positions, join them and label the image.

What is the coordinate rule for a rotation of $180^\circ$ about the origin?

$(x,y)\to(-x,-y)$.

Which point is always invariant under a rotation?

The centre of rotation.