Drawing a Circle

In this lesson we are going to develop a function that uses a turtle to draw a circle. As we develop this function we will investigate several problem solving strategies that illustrate how computer scientists think as they solve problems.

In figuring out how to write this function we must realize that there are some limitations of our ability to draw a circle. First, we are limited by the turtle functions we already know about, for example, left, right, forward. There is not a method for drawing a curved line with a turtle (well, actually there is, but we’re not going to use it).

One of the first strategies we will employ is called simplification. Let’s look at something simpler than drawing a circle and see what we can learn, as we look at some simpler examples we’ll try to generalize what we learn to help us build a more complex function.

One thing we already know how to do is to write a function to draw a square. Now a square doesn’t look anything like a circle, but maybe if we look at some other simple shapes that will help us. Just to remind you, here is the code for the drawSquare function.

Although this isn’t going to do anything if you click on the run button, you could fill in the rest of the code to make it work, right?

Now, see if you can modify the code for drawSquare to make it draw a triangle. Call this new function drawTriangle When you finish drawTriangle write a third function called drawOctagon. When you are finished follow the link below to the next part of this lesson.

OK, they work now

Next Section - Lessons from a Triangle