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4-2 Sexagesimal and circular measure

4-2 Sexagesimal and circular measure

Point 2 of 11 — Unit 4: Trigonometry — Directed Angles, Functions, Related Angles and GraphsQuestion bank: 0 questions (0 with pictures)

02 4-2 Sexagesimal and circular measure

  • Degree: 1/360 of one revolution; 1° = 60′, 1′ = 60″, so 1° = 3600″.
  • Decimal degrees to DMS: keep the integer part as degrees, multiply the fraction by 60 for minutes, then again by 60 for seconds.
  • The radian is the angle whose intercepted arc equals the radius; one revolution = 2π radians, hence π rad = 180° and 1 rad ≈ 57.3° ≈ 57°16′.

Conversion

  • Degrees → radians: multiply by π/180. Radians → degrees: multiply by 180/π.
  • Common values: 30° = π/6, 45° = π/4, 60° = π/3, 90° = π/2, 120° = 2π/3, 135° = 3π/4, 150° = 5π/6, 210° = 7π/6, 270° = 3π/2, 360° = 2π.
  • Never mix units inside one expression — convert everything first, and leave the answer in the unit the question asks for.

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