Trigonometric Functions: Background You’ll Need 3

  • Find the radius and diameter of a circle

radius and diameter

A radius is the distance from the center of the circle to any point on the circle.
A diameter is twice as long—it stretches all the way across the circle through the center.

[latex]\text{Diameter} = 2r \quad \text{and} \quad r = \frac{d}{2}[/latex]

  1. Find the diameter if the radius is [latex]7[/latex] cm.
  2. Find the radius if the diameter is [latex]18[/latex] inches.

The radius is always half the diameter, and the diameter is always twice the radius.