Rotate 90 Degrees Around A Point That Is Not The Origin

🔑 Key Concepts

  • When the center of rotation is not the origin, first translate the center of rotation to the origin.
  • Apply the standard rotation rule around the origin.
  • For a \(90^\circ\) clockwise rotation around the origin, use \((x,y)\rightarrow(y,-x)\).
  • After rotating, translate the figure back to the original center of rotation.
  • Rotations preserve shape and size, so the image is congruent to the original figure.

✏️ Worked Examples

🧠 Math Vocabulary

  • Rotation: A transformation that turns a figure around a fixed point.
  • Center of rotation: The fixed point that a figure rotates around.
  • Clockwise: A turn in the same direction as the hands of a clock.
  • Preimage: The original figure before a transformation.
  • Image: The new figure after a transformation.
  • Congruent figures: Figures with the same size and same shape.

💡 Main Idea

To rotate around a point that is not the origin, temporarily shift the center of rotation to the origin, apply the rotation rule, and then shift the rotated figure back.

📚 What You Should Already Know

Students should know how to plot points, identify coordinates, translate points on the coordinate plane, and use basic rotation rules around the origin.

🚀 What Comes Next

Students can extend this process to other centers of rotation, counterclockwise rotations, \(180^\circ\) rotations, and combinations of transformations on the coordinate plane.

🧩 Embed This Video in Your LMS

Teachers can embed this YouTube video directly into Canvas, Google Classroom, Schoology, or another learning platform. Click below to show the embed code.