Every profession has particular tools that they use all the time, a chef has their knives, the sewer a machine and the mathematician, well they have their construction tools.
No, not hammers and hard hats - Mathematicians use a compass, pencil and a ruler.
From just these three things we can create (nearly) all of what we require in geometry.
A great Greek mathematician named Euclid, who is credited to have written the first mathematics textbook over 2000 years ago, went to great lengths to detail many of the mathematical constructions we will look at today. Geometrical constructions were so important to mathematics at the time because most problems were solved graphically, not arithmetically.
Use the above steps to construct a circle with radius of 3\text{ cm}.
Use the above steps to construct a circle with radius of 2 \text{ cm}.
Use the above steps to construct a circle with diameter of 5\text{ cm}.