In mechanics, when we talk about a vector's direction, the cosines l, m, n are just the cosines of the angles it makes with x, y, z axes. The sum of their squares is 1 because it comes from cos²α + cos²β + cos²γ = 1, a trigonometric identity. But, baba, in real life on these narrow roads, your "direction cosines" are just the auto-wallah's sudden turns—my Amaze's alignment is never by the book! I trust my instinct more than these ratios; after all, I reached college today, na?
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