Lines and line segments are not the only geometric figures that can form tangents. Tangents, of course, also allude to writing or speaking that diverges from the topic, as when a writer goes off on a tangent and points out that most farmers do not like having their crops stomped down by vandals from this or any other world. The word "tangent" comes from a Latin term meaning "to touch," because a tangent just barely touches a circle. Crop circles almost always "appear" very close to roads and show some signs of tangents, which is why most researchers say they are made by human pranksters. That would be the tiny trail the circle makers walked along to get to the spot in the field where they started forming their crop circle. In our crop circle U, if we look carefully, we can see a tangent line off to the right, line segment FO. To do that, the tangent must also be at a right angle to a radius (or diameter) that intersects that same point. What is a tangent?Ī tangent is a line (or line segment) that intersects a circle at exactly one point. A tangent connects with only one point on a circle. A chord and a secant connect only two points on the circle. Notice that the diameter connects with the center point and two points on the circle. Here is a crop circle that shows the flattened crop, a center point, a radius, a secant, a chord, and a diameter: Tangent to a circle Secant (a line passing through two points of the circle)ĭiameter (a chord passing through the center)Ĭircumference (the distance around the circle itself. Radius (the distance from the center to the circle)Ĭhord (a line segment from the circle to another point on the circle without going through the center) A circle has a center, which is that point in the middle and provides the name of the circle. This means a circle is not all the space inside it it is the curved line around a point that closes in a space. The diameter is a special type of chord that goes through the center point of the circle.Circles are the set of all points a given distance from a point. Sort of like a piece of pizza or pie.Ĭhord - A chord is a line segment that joins two points on the circle. Other Circle Geometry terms Sector - A sector is a section of the circle made by two different radii. Where c = circumference, d = diameter, and r = radius. It's close enough.īack to circumference There are a few handy formulas we will use: The decimals actually go on for a long time (forever), but we will round it off to 3.14. We won't go into the details right now, but let's just agree to use it and that it works for now. It stands for a number that we use with circles. We use the following formula to figure the circumference: So the diameter is two times the radius and the radius is one half of the diameter.Ĭircumference - The circumference is the distance around the circle. This gives you our first math equation for the circle: This is the same distance R we used to make the circle in our definition.ĭiameter - The diameter is a straight line that goes across the circle and through the center. Terms used in circle geometry Radius- The radius is the distance from the center point to the edge of the circle. Watch as we add in equal distanced points in the movie below: Now pick all the other points on the screen that are the exact same distance R away from point P. Let's pick a point on a flat surface, like this screen, for instance. Okay, so let's start out with the "given point". We can learn a lot about the real world and how it works by understanding circles.įirst, what is the official definition of a circle?Ī circle is a shape that is made up of all the points on a plane (a flat surface) that are the same distance from a given point. There are circles all around us in the real world. A circle is an important shape in geometry.
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