Number keys; Logo - Zero heading and marking angles

VOCAB QUIZ TOMORROW!!

To start with, type all lines once from p. 30, 13D, lines 1-8.

Next we will learn the 5 (L1) and the 7 (R1).  These will actually be two of the easier numbers to learn.

After learning these two numbers we will again be working with Logo.  There are several new concepts we need to introduce today.  First, let's review - when your turtle is pointed up on your screen we call this Zero heading (to get to this point you can type in HOME - another primitive).  You should also remember FORWARD and BACK (these primitives move the turtle), as well as LEFT and RIGHT (these primitives turn, or rotate, the turtle).  We also erased everything we typed on our screen by typing in CLEARSCREEN.

Other primitives we did not talk about yesterday but need to cover are:  HIDETURTLE, SHOWTURTLE,  PENUP, and PENDOWN.  These should be fairly easy to understand; you would want to use HIDETURTLE when you want to see your screen without the turtle, and then you would use SHOWTURTLE to get your turtle back on your screen.  PENDOWN is how Logo starts - the pen is down and your turtle is in "drawing" mode; however, if you want to move your turtle without drawing lines you can use the PENUP command.

One of the aspects of Logo that we can use are the abbreviations for these primitives.  They are as follows:  FD, BK, RT, LT, HOME (sorry - no abbreviation), CS, HT, ST, PU, and PD.

Today we are going to discuss the marking angles in Logo.  It's important to remember several key mathematical concepts.  First, a complete circle, or TOTAL TURTLE TRIP as it is referred to in Logo language, is 360 degrees.  If you stood facing a direction, turned around one complete time, you would have turned 360 degrees.

Secondly, you can turn either right or left to get to the same "point"- it doesn't matter.  For example, say we want to turn RIGHT 90; in order to find out how far the turtle would have to turn left you just subtract the 90 from 360 (why 360?  Because that is one TOTAL TURTLE TRIP!).  Therefore, to get to the same point (or more accurately, angle) you could turn LEFT 270.

Lastly, we need to understand a couple of things about polygons.  The sum of the interior angles of a triangle add up to be 180.  What are the interior angles of an equilateral triangle?  You can use simple division to figure this out.  Also, the sum of the interior angles of any quadrilateral are 360.  For each additional side to a polygon you will add 180 degrees of angles (in other words, a 5-sided figure would have 540 degrees of angles; a 6-sided figure would have 720 degrees of angles, and so on).