Mathematical Illusions A Lesson in the Math Fun

Mathematical Illusions A Lesson in the “Math + Fun!” Series Apr. 2007 Mathematical Illusions 1

About This Presentation This presentation is part of the “Math + Fun!” series devised by Behrooz Parhami, Professor of Computer Engineering at University of California, Santa Barbara. It was first prepared for special lessons in mathematics at Goleta Family School during four school years (2003 -07). “Math + Fun!” material can be used freely in teaching and other educational settings. Unauthorized uses are strictly prohibited. © Behrooz Parhami Apr. 2007 Edition Released First Apr. 2007 Revised Mathematical Illusions Revised 2

Things May Not Be What They Seem Do you see circles or spirals? Apr. 2007 Are some of the squares bigger? Mathematical Illusions 3

Activity 1: Appearances May Be Deceiving 1. Which of the two vertical lines is longer? 2. Which of the two white squares is larger? 3. Draw a 9” 11” rectangle and cut it along the dashed line, as shown. Slide the lower piece down and to the left. Cut out the small triangle that sticks out at the lower left and use it to fill the opening at the upper right. You get a 10” square. Apr. 2007 Explain how the area of the figure increased from 99 to 100. Mathematical Illusions 4

Activity 2: Does 64 Equal 65? Cut out an 8” square as shown and rearrange the pieces to form a 5” 13” rectangle, thus proving 64 = 65. What is wrong with this? Apr. 2007 Mathematical Illusions 5

Hiding Pictures Within Pictures Find the man’s face. What’s hiding in the trees? Apr. 2007 Mathematical Illusions 6

Morphing and Mutation Apr. 2007 Mathematical Illusions 7

Morphing Images on a Computer See “Tiger Face Morph” and other video clips at: http: //creativesam. tfcentral. com/Animations. html Apr. 2007 Mathematical Illusions 8

Illusion of Motion Apr. 2007 Mathematical Illusions 9

Ambiguous Images A Do you see a vase or two faces? Man playing saxophone or girl’s face? Apr. 2007 Stairs: top side or bottom side? Rabbit or bird? Mathematical Illusions B Is Point A closer to us than B or further back? Young woman or old woman? 10

What Do You See in These Pretty Patterns? Fix your stare at a specific point and describe what you experience. Repeat the process, this time slowly moving your head back and forth. Apr. 2007 Mathematical Illusions 11

Impossible Designs Apr. 2007 Mathematical Illusions 12

Impossible Objects Swedish stamp How many legs does this elephant have? Apr. 2007 Mathematical Illusions 13

Illusion of Distortion Horizontal lines appear slanted in the middle portion of the diagram Vertical lines appear crooked, but they are perfectly straight Apr. 2007 Which line on the left is a continuation of the on the right? Mathematical Illusions 14

3 D Illusions Apr. 2007 Mathematical Illusions 15

Illusion of Distortion or Deformation The figure on the right spins when you view this page in a slide show. Notice how the shape is deformed as it spins. Apr. 2007 Mathematical Illusions 16

Activity 3: Experiencing Distortion In each of the following diagrams, use a ruler and pencil to connect the black dots on either side using two horizontal lines. Explain what you see. Apr. 2007 Mathematical Illusions 17

Activity 4: Where Does the Sixth Box Go? Cut along the dashed line. . . and shift the bottom half to left, as shown below. What happened to one of the boxes? Apr. 2007 Mathematical Illusions 18

Activity 5: Making People Appear and Disappear 1. Count the people in the picture to the right and write the number down. 1 2 2. The upper half of the picture is redrawn below. Cut out the rectangular pieces 1 and 2 by cutting along the dashed lines. 3. Now, put the two cut-out pieces in reverse order on the picture above, covering the original pieces (piece 1 on the right and piece 2 on the left). 3 1 2 4. Recount the number of people and explain what happened. 3 Apr. 2007 Mathematical Illusions 19

Next Lesson Late May or early June 2007 Apr. 2007 Mathematical Illusions 20