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4.3 E) Rotation: Finding
4.3 E) Rotation: Finding
In this section we are going to have a look at finding the rotation of the shape. I am going to go through the working by using an example.
Click here for a printable version of the questions in this section.
Click here for a printable version of the questions in this section.
Example 1
Shape A on the diagram below has been rotated 90° clockwise to create shape B. Find the centre of rotation.
Shape A on the diagram below has been rotated 90° clockwise to create shape B. Find the centre of rotation.
The first step in answering a question like this is to find the respective points on the original shape and the rotated shape. I have labelled the two respective points that I am going to choose on the diagram below.
We are told that the shape has been rotated 90° clockwise, which is a quarter of a full turn in a clockwise direction. I am going to draw a quarter a circle connecting the respective point.
I am now going to continue the quarter of the circle to create a full circle and the full circle is shown below.
The centre of this circle will be the centre of rotation and the centre of the circle is (1, 2).
Therefore, the centre of rotation for this question is (1, 2).
It is then a good idea to use tracing paper to check whether we have obtained the correct centre of rotation. For this question, we would rotate shape A 90° clockwise around the point (1, 2). We would then check that the outcome of our rotation is shape B.
It is then a good idea to use tracing paper to check whether we have obtained the correct centre of rotation. For this question, we would rotate shape A 90° clockwise around the point (1, 2). We would then check that the outcome of our rotation is shape B.
Another method
A second method to answer a question like this is to trace the shape out on a bit of tracing paper. We then take an educated guess at the centre of rotation and rotate the shape by what we are told in the question. We then compare the outcome of our rotation against what the outcome should be (we compare the outcome that we get against shape B). We continue guessing the point of rotation until the rotation from the centre of rotation that we have found gives us the rotated shape in the question (shape B).
A second method to answer a question like this is to trace the shape out on a bit of tracing paper. We then take an educated guess at the centre of rotation and rotate the shape by what we are told in the question. We then compare the outcome of our rotation against what the outcome should be (we compare the outcome that we get against shape B). We continue guessing the point of rotation until the rotation from the centre of rotation that we have found gives us the rotated shape in the question (shape B).