Mathematics
A(4, -1), B(0, 7) and C(-2, 5) are the vertices of a triangle. △ABC is reflected in the y-axis and then reflected in the origin. Find the coordinates of the final images of the vertices.
Reflection
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Answer
The graph for this problem is shown below:

First the triangle is reflected in y-axis.
We know that,
Rule to find reflection of a point in y-axis :
- Change the sign of abscissa i.e. x-coordinate.
- Retain the ordinate i.e. y-coordinate.
∴ Coordinates of
⇒ A(4, -1) on reflection in y-axis becomes A'(-4, -1).
⇒ B(0, 7) on reflection in y-axis becomes B'(0, 7).
⇒ C(-2, 5) on reflection in y-axis becomes C'(2, 5).
Now the triangle is reflected in origin.
We know that,
Rules to find the reflection of a point in the origin :
- Change the sign of abscissa i.e. x-coordinate.
- Change the sign of ordinate i.e. y-coordinate.
∴ Coordinates of
⇒ A'(-4, -1) on reflection in y-axis becomes A''(4, 1).
⇒ B'(0, 7) on reflection in y-axis becomes B''(0, -7).
⇒ C'(2, 5) on reflection in y-axis becomes C''(-2, -5).
Hence, the coordinates of the final images of the vertices are (4, 1), (0, -7) and (-2, -5) respectively.
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Related Questions
The point P(a, b) is first reflected in the origin and then reflected in the y-axis to P'. If P' has coordinates (3, -4), evaluate a, b.
A point P(a, b) become (-2, c) after reflection in the x-axis, and P becomes (d, 5) after reflection in the origin. Find the values of a, b, c and d.
The points A(4, -11), B(5, 3), C(2, 15) and D(1, 1) are the vertices of a parallelogram. If the parallelogram is reflected in the y-axis and then in the origin, find the coordinates of the final images. Check whether it remains a parallelogram. Write down a single transformation that brings the above change.
Use a graph paper for this question (take 2 cm = 1 unit on both x and y axes).
(i) Plot the following points : A(0, 4), B(2, 3), C(1, 1) and D(2, 0).
(ii) Reflect points B, C, D on y-axis and write down their coordinates. Name the images as B', C', D' respectively.
(iii) Join points A, B, C, D, D', C', B' and A in order, so as to form a closed figure. Write down the equation of line of symmetry of the figure formed.