Mathematics
The point P(-7, 9) is rotated through 90° about origin in the anticlockwise direction to get point Q. If Q is reflected in y-axis to point R, write the co-ordinates of Q and R.
Symmetry
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Answer
When a point P(x, y) is rotated through 90° (anticlockwise) about the origin O, we get the point P' = (-y, x).
Reflection of P(-7, 9) in origin = Q(-9, -7).
When a point is reflected in y-axis, the sign of its x-coordinate (abscissa) changes.
Reflection of Q(-9, -7) in y-axis = R(9, -7).
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