Three Dimensional Geometry
💡 Direction Cosines and Direction Ratios
• Direction Angles (α, β, γ): Angles a line makes with positive X, Y, and Z axes. • Direction Cosines (l, m, n): Cosines of direction angles: l = cos α, m = cos β, n = cos γ. • Key Relation: l² + m² + n² = 1. • Direction Ratios (a, b, c): Numbers proportional to direction cosines, such that l/a = m/b = n/c.