Direction ratios and direction cosines
Three-dimensional geometry and vector algebra · Mathematics
Study notes
Q: Find the direction cosines of the line joining (1,2,3) to (4,6,8). Direction ratios: (3, 4, 5). Magnitude = √(9+16+25) = √50 = 5√2. l = 3/(5√2), m = 4/(5√2), n = 5/(5√2) = 1/√2. Check: 9/50+16/50+25/50 = 1 ✓.