Robot reciprocal of Pithagorean
- Rafael Losada Liste
This activity belongs to the GeoGebra book Attractive projects. Until now, the behavior of the robots was determined by vectors defined by other points. In this last section, we will create robots that, before undertaking a movement, find out what is happening around them and, based on the values obtained, make a decision. 2D project: create automatic dynamic demonstrations. In this example, we want to demonstrate the reciprocal of the Pythagorean theorem. We start from a triangle ABC and call dif the expression abs(a² + b² - c²). Our goal is that dif is worth zero. We create a slider t that will serve to animate the vertex C (to which we have activated the trace), so that it varies quite frequently, for example, between 0 and 1 with step 0.01. Another slider inc, between 0 and 0.1, will help us to establish the progress in each step. In principle, the value of inc will be 0.1. Finally, we create two auxiliary objects: C0 = (0,0) and dif0 = 0 that will be valid to maintain, respectively, the current values of C and dif. Now we write the program of our robot. Each time the value of t is updated, the following instruction script will be executed (the # symbol is used to add comments): # We set the starting values dif0 and C0: SetValue(dif0, dif) SetValue(C0, C) # We vary C and compare the difference of the NE with dif0: SetValue(C, C + (inc, inc)) SetValue(C, If(dif<dif0, C, C0)) Valor(C0, C) # [We repeat these three instructions for the movements towards E, SE, S, SW, W, NW and N, that is, (inc, 0), (inc, -inc), (0, -inc), (- inc, -inc), (-inc, 0), (-inc, inc) and (0, inc).] # If the difference is not reduced, we increase the precision by dividing inc by 10: SetValue(inc, If(dif == dif0, inc / 10, inc)) # When the difference is zero, robot stops (in addition, the message "process done" will be displayed): Yes (dif == 0, StartAnimation(false)) We just have to animate the slider t. Note: If we want to repeat the experiment again, we must remember to return inc to the value 0.1.