radius

Noun:

• a straight line from the centre of a circle or sphere to the circumference.
• a line segment joining the centre of a circle or sphere with any point on the circumference.
• a bone of the forearm, extending from the elbow to the wrist.

The word "radius" comes from the Latin word "radius", which means "ray".

The first recorded use of the word "radius" in English was in the 14th century.

Why might it be useful to know the radius of a circle?

Question:

Define the term "radius" in the context of geometry and explain its significance in measuring and describing circles.

Answer:

In geometry, the "radius" of a circle is a fundamental measurement that refers to the distance from the centre of the circle to any point on its circumference. It is denoted by the letter "r." The radius is a key property of circles and plays a crucial role in understanding their properties and relationships.

The radius is significant in various ways. First, it determines the size of the circle. The longer the radius, the larger the circle's diameter and circumference. Additionally, the radius helps define the circle's area through the formula A = πr², where "A" represents the circle's area and "π" is a mathematical constant (approximately 3.14159).

Furthermore, the radius aids in measuring distances within the circle. It allows us to calculate the length of arcs and the curvature of circular segments. Moreover, the radius, along with the centre, helps in constructing circles and analyzing their geometric properties.