reentrant angle

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Word: Reentrant Angle

Part of Speech: Noun

Definition: A reentrant angle is an interior angle of a shape, specifically a polygon, that measures more than 180 degrees. This means that when you look at the angle from the inside of the shape, it opens inward rather than outward.

Explanation:

Imagine a square. All the angles inside a square are 90 degrees, which means they are not reentrant. Now, think about a shape like a star or a certain kind of zigzag. When the corners of that shape bend inward so much that the angle created is greater than 180 degrees, that is a reentrant angle.

Usage Instructions:

• Use "reentrant angle" when discussing shapes, especially in geometry or design.
• It is mainly used in mathematical contexts, so it may not come up often in everyday conversation.

Example:

• "In this polygon, the corner bends inward, creating a reentrant angle that measures 210 degrees."

Advanced Usage:

In more advanced geometry, reentrant angles can be important when studying concave polygons, where at least one angle is greater than 180 degrees. Understanding how to identify and work with reentrant angles can help in calculating area, perimeter, and other properties of complex shapes.

Word Variants:

• Reentrant: This can be used as an adjective to describe something that has reentrant angles.
• Concave Polygon: A type of polygon that can have reentrant angles.

Different Meaning:

In other contexts, "reentrant" might refer to something that can return or re-enter. For example, in computer programming, a "reentrant function" is one that can be called again before its previous executions are complete.

Synonyms:

• Concave angle (though this term can refer to any angle that opens inward, not just those over 180 degrees).

Idioms and Phrasal Verbs:

There are no common idioms or phrasal verbs specifically associated with "reentrant angle." However, learning about angles might lead to idioms involving "sharp angles" or "bending the rules," which have different meanings.

Summary:

A reentrant angle is an important concept in geometry, referring specifically to angles greater than 180 degrees in polygons.

Academic

Noun

1. an interior angle of a polygon that is greater than 180 degrees

Synonyms

• reentering angle