4 Vocabulary Tessellation- a repeating pattern of figures that Completely covers a plane without any gaps or overlapsEdge- the intersection between two bordering tilesVertex- the intersection of three or more bordering tilesRegular tessellation- when a tessellation uses only one type of regular polygon to fill up a planeSemi-regular tessellation- when a tessellation uses more than one type of regular polygon to fill up a planeTranslational symmetry-when a translation maps that tessellation onto itself
5 Vocabulary (continued) Glide reflectional symmetry-when a glide reflection maps the tessellation onto itselfReflection or line symmetry-when a figure is reflected across the axis & the image is the same as the originalRotational symmetry-when a rotation of 180 degrees or less is performed on a tessellation and the resulting image is the same as the original imagePoint symmetry-when a tessellation rotates 180 degrees and the image is the same
6 Determining which polygons to tessellate or not To see which regular polygons can tessellate or not you use the following formula to find the polygon’s angle measurea=180(n-2)/nIf the angle measure is a factor of 360, then that polygon can tessellateFor example, if you wanted tosee if a regular pentagon, like the oneat the right, could tessellate, you usethe formula to find that each innerangle is 108 degreesThen you would divide 360 By 108360/108=3 1/3, therefore a regular pentagon cannot tessellate
7 Tessellations Activity Johnson wants to tile the floor of his house. However he wants to semi-tessellate the tiles with 3 different shapes. Can you help Johnson pick which shapes he needs?
9 VocabularyReflection – a transformation which uses a line that acts like a mirror, with an image reflected in the lineLine of Reflection – the line which acts like a mirror in a reflectionLine of symmetry – the imaginary line where you could fold the image and have both halves match exactlyIsometry – a transformation that preserves length, after the shape is reflected, its corresponding sides remain congruentLine of symmetry
10 Reflecting Figures & Finding the Line of Reflection Rules for reflecting figures:rx-axis (x,y)=(x,-y)ry-axis (x,y)=(-x,y)ry=x (x,y)=(y,x)ry=-x (x,y)=(-y,-x)ry=n (x,y)=(x,2[n-y]+y)rx=n (x,y)=(2[n-x]+x,y)When finding the line of reflection onecould use the midpoint formula. Themidpoint of each pair of corresponding pointsis a point on the line of reflection.In the problem to the right, where is the lineof reflection?
11 Finding the Minimum Distance To find the minimum distance one must first reflect point A over the givenline.Then a segment betweenA’ & B should be drawn.The point where segment A’Bintersects the line ofreflection is point C.Then a segment from A to Cshould be drawnSegment AC is congruentto segment A’CIn this problem, the mayor of Haemmerle Ville wants a new library built that has the minimum distance from Rite Aid, the town’s beloved pharmacy & the school playground.In this problem, the mayor of Haemmerle Ville wants a new library built that has the minimum distance from Rite Aid, the town’s beloved pharmacy & the school playground.
12 ActivityTake the paper that you have and bring the top left tip to the right side of the paper till a triangle is made.Then fold the small rectangle under the triangle. You now have a square!Fold the square in different ways to find how many lines of symmetry the square hasHow many lines of symmetry does a square have?This proves that a regular polygon’s number of lines of symmetry is equal to it’s number of sides
14 What is a Dilation?A dilation is a transformation that reduces or enlarges a polygon by a given scale factor around a given center point.When a figure is dilated the new figure will always be similar to the original figureCenter PointThere is ascale factorof 2 whichmeans thatthe new figureis 2 times larger
15 The Scale FactorThe scale factor is the amount by which the image grows or shrinksTo find the scale factor of two given shapes simply find two corresponding sides or points and put the new shape’s side over the original shape’s corresponding side.15Here the scale factor is 3 because 15 is the new distanceand 5 is the old distance. 15/5 = 35
16 Reductions and Enlargements If the scale factor of your dilation is greater than 1 than the dilation is an enlargement.If your scale factor is greater than 0 but less than 1 than the dilation is a reductionThis is an enlargement because the scale factor is 5.10020
17 ActivityJohnny wants to make a scale model of the clock tower big ben in London. If he wants to make it 1/100 of the actual height how tall will the scale model be?316 ft.
19 Key Vocabulary Rotation A transformation where a figure is turned around a center of rotation.IsometryA transformation where the figure stays congruentCenter of RotationA fixed point anywhere that the figure rotates about. The center of rotation can be anywhere. It can be inside or outside the figure.Angle of RotationThe angle created by rays drawn from the center of rotation to a point and its image.
20 Key ConceptsTheorem Line K and line M intersect at point P. Then a reflection in line K and the line M is a rotation about point P. The angle of rotation is double the angle formed by K and M. Since the angle formed by lines Kand M is 70°, the angle of rotation is 140°.
21 Key Concepts Cont. Rotational Symmetry Equations: A figure in the plane has rotational symmetry if the figure can be mapped onto itself by clockwise rotation of 180 degrees or less.Equations:R90 (X,Y) = (-Y,X)R180 (x,y) =( -x,-y)R270 (x,y) =(y,-x)R-90 (x,y) = (y, -x)
22 Rotational SymmetryDoes this figure have rotational symmetry? If so, what is the angle of rotation?The building has 36 sides so it has a rotational symmetry of 10°
23 Rotating on a Coordinate Plane You can rotate the building by using the equations from the previous slide. You are to rotate counter clock wise unless told by the problem.Equations:R90 (X,Y) = (-Y,X)R180 (x,y) =( -x,-y)R270 (x,y) =(y,-x)R-90 (x,y) = (y, -x)
24 Real- Life Application The Pentagon has a rotational symmetry of 72° When it is rotated at 72°, it maps onto itself.
25 Save the Leaning Tower of Pisa! It is 3025 and the leaning tower of Pisa is now leaning too much. Now, the people decide that there is a need to reconstruct the tower. Find the angle you need to rotate the leaning tower to make the tower perpendicular to the ground by using a protractor.
27 Vocab Vector --A quantity having direction as well as magnitude Initial point – starting point of the vectorTerminal point – ending point of the vectorComponent form/ coordinate vector– horizontal and vertical values < a, b >Coordinate notation– (x,y) (x+a, y+b)
28 Andi’s explanation It’s pretty much a thing move to another place. See example: A house moved to a park from a city by a witch. ( not in scale)Vector component form/ coordinate vector: (15, 3)Coordinate notation– (x,y) (x+15, y+3)315
29 Relating to the WorldMobile houseA movinghouseAnothermoving
30 practice Make the house transfer 10 boxes to right and 5 boxes up. Vector component form/coordinate vector: (10, 5)Coordinate notation– (x,y) (x+10, y+5)practiceMake the house transfer 10 boxes to right and 5 boxes up.