Line of symmetry
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There were questions where you used the Tell Me button.ĭevelopment, we find any feedback extremely valuable. State the order of rotational symmetry and the number of lines of symmetry for each of the following shapes:ĭescribe the symmetries of the shapes shown below:ĭescribe the symmetry properties of each of the following triangles: Once you have checked these with the button, fill in the order of rotational symmetry for each one and check that too. If you make a mistake, press the delete key and the grid will be cleared.įor each of the six diagrams below, draw on all the lines of symmetry and mark the centre of rotation point. When you let go of the button the line will appear and it will automatically cross the whole grid. The left mouse button at one point on the line and drag the pointer to another point on the line.
To plot a point, just click on the grid with your left mouse button. NOTE: In the next question you need to plot points and draw lines on grids. If you can't work out the right answer then click on On to clear your original answer and have another go. Then will appear and you should move on to the next Click on theīutton to find out whether you have answered correctly. Work out the answers to the questions below and fill in the boxes. The order of rotational symmetry and the number of lines of symmetry of any regular polygon is equal to the number of sides. You can see that there are seven lines of symmetry, and the regular heptagon also has rotational symmetry order seven. A heptagon is a shape with seven sides and this one has equal sides and equal angles. Note how they all rotate around a cross - this is the center of rotation. One has an order of rotational symmetry of 1, one has order 2, and the other one has order 4.Ĭlick on the shapes to see them rotate and count how many times they look the same in one turn. The three diagrams below show shapes with different orders of rotational symmetry. There can only be one centre of rotation in a shape. There is a centre of rotation about which the rotational symmetry occurs. The order of rotational symmetry is the number of times an object looks the same as it did originally when it is rotated through 360°.Įven if a shape appears to have no rotational symmetry then the order of rotational symmetry will still be 1, because every shape looks the same at the end of a 360° rotation as it did originally. Here are the shapes with the lines of symmetry drawn on:Īn object has rotational symmetry if it looks the same as it did originally when rotated. In (b) there are also two lines of symmetry, both diagonal. In (a) there are two lines of symmetry, one horizontal and one vertical. Look for lines of symmetry in the two shapes below: The line the object is reflected across is called a line of symmetry or a mirror line. A line of symmetry is known as a rigid motion (or transformation) in geometry since the figure that is reflected across it does not change size or shape and is only 'flipped' across the line of symmetry. There are two types of symmetry: reflective symmetry and rotational symmetry.Īn object has reflective symmetry if it can be reflected in a particular line and looks the same as the original. In this section we revise the symmetry of objects and examine the symmetry of regular polygons. If you want to change the planes of symmetry in an existing symmetry group, click Object Symmetry Edit Symmetry.Unit 15 Section 3 : Symmetry Unit 15 Section 3 : Symmetry For more information, see To set up the planes of symmetry. To add more symmetry lines for a more complex symmetry group, type a number in the Mirror lines box on the property bar. To create a mirror symmetry group from scratch You can create a symmetry group from multiple shapes and curves. You can also create a symmetry group from an object by right-clicking the object and clicking Create New Symmetry. To do this, select the object, double-click the Outline icon in the lower-right corner of the application window, and in the Outline Pen dialog box, enable the Scale with object check box. To accurately mirror an object that has a calligraphic outline, you must first link the outline thickness to the object’s size. To create a symmetry group from objectsĬlick Object Symmetry Create New Symmetry.Ī symmetry line appears in the drawing window, and the primary object is duplicated and mirrored.Įdit the primary object or add more objects.Ĭlick Object Symmetry Finish Editing Symmetry.
#LINE OF SYMMETRY HOW TO#
From left to right: Default symmetry line, adding a symmetry line, rotating the symmetry lines.įor information about how to edit symmetry groups, see Editing symmetry groups. In mathematics, symmetry has a more precise definition, and is usually used to refer to an object that is invariant under some transformations including.