Angle measurement: π (PI). Radians. Degrees. Definitions

π (PI). Radians. Degrees. What are they and how to use them?

Three definitions on π (PI). Radians. Degrees



  • Three definitions on π (PI), Radians, Degrees. Angle measurement

  • π (PI)

  • Definition: π represents the constant ratio of a circle's circumference (circle's length), C, to its diameter, d (d = 2 × r, where r is the radius of the circle).
  • π is approximately 3.14159, commonly estimated as the fraction 22/7.
  • π = C/d = C/(2 × r)
  • Angle measurement: π. Radians. Degrees

    Angle measurement: π. Radians. Degrees

  • Radians

  • Definition: A radian is a standard unit of angle measurement. A radian is equal to the angle formed when the length of the arc of a circle is equal to the radius of the same circle.
  • There are exactly 2π radians in the circumference (the length) of a circle (any circle).
  • 1 radian is roughly 57.296° (degrees).
  • An angle of 360° = 2π radians, 180° = π radians, 90° = π/2 radians, 45° = π/4 radians.

  • Degrees

  • Definition: Angles are usually measured in degrees (°). A degree is a standard unit of angle measurement.
  • The angle formed by a complete circle is 360°.
  • An obtuse angle has a measure between (90° and 180°). A right angle is 90°. An acute angle has a measure between (0° and 90°).