The first proportional compasses were developed in the late 16th century, including a popular version invented by Galileo. Many refinements and improvements were made over the years, allowing the compass to be used for a variety of mathematical and geometric calculations. In its simplest form, it is used to trace circles and arcs on paper, but these figures can be used to solve problems related to geometry and math. One of these is how to find the midpoint of a line.
Instructions
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1
Place the needle of a compass on one endpoint of the line.
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2
Adjust the hinge of the compass so that the pencil end extends more than half the distance to the opposite endpoint of the line.
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3
Draw a circle.
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4
Place the needle of the compass on the opposite endpoint and, without adjusting the hinge, trace a second circle.
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5
Align a ruler to join the two points where the circles intersect and trace a line between them. This line exactly intersects the midpoint of the first line.