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Direction cosines or direction ratios?

Exercise and reference answers

Items
  1. Item
    Written l, m, n
    Category
    Direction cosines
  2. Item
    Satisfy l² + m² + n² = 1
    Category
    Direction cosines
  3. Item
    Are actual cosines of angles
    Category
    Direction cosines
  4. Item
    Written a, b, c
    Category
    Direction ratios
  5. Item
    Any proportional triple will do
    Category
    Direction ratios
  6. Item
    Need dividing by √(a²+b²+c²) to normalise
    Category
    Direction ratios
Categories
  1. Item
    Direction cosines
  2. Item
    Direction ratios

Explanation

Cosines are fixed and normalised ratios are any proportional triple. Source: syllabus Maths Part II, Ch 11 Three Dimensional Geometry.
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