Page 1 - Lesson Notes
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SAI International School
CLASS - IX
Mathematics
CHAPTER-3: Coordinate Geometry-2 Lesson Notes-2
SUB TOPIC: Mirror Image
What is a Reflection in Math?
In real life, we think of a reflection as a mirror image, like when we look at our own
reflection in the mirror. This idea of reflection correlating with a mirror image is
similar in mathematics.
Definition: Reflection over the X- Axis
A reflection of a point, a line, or a figure in the X axis involved reflecting the image
over the x axis to create a mirror image. In this case, the x axis would be called the
axis of reflection.
When a point is reflected across the X-axis, the x-coordinates remain the same. But the Y-
coordinates are transformed into its opposite signs.
Therefore, the reflection of the point (x, y) across X-axis is (x, -y).
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