A rotation turns a shape about a fixed point called the centre of rotation.
Default centre: (0, 0).
Rotation Rules (About the Origin)
|
Rotation |
Mapping |
|
90° anticlockwise |
(x, y) → (−y, x) |
|
90° clockwise |
(x, y) → (y, −x) |
|
180° |
(x, y) → (−x, −y) |
|
270° anticlockwise = 90° clockwise |
(x, y) → (y, −x) |
Worked Example 1
Rotate A(3,2) 90° anticlockwise about the origin.
New point: (−2, 3)
Worked Example 2
Rotate A(4,-5) , B(2,-5), C(5,-2) and D(4,-5) 90° about the origin in a clockwise direction.
New point: P(-5,-4) , Q(-5,-2), C(-2,-5) and D(-2,-1)