We have, (3,4,∞) Distance of point to X-axis =√16+α2 Distance of point to Y-axis =√9+α2 Distance of point to Z-axis =√9+16=5 Sum =S=√16+α2+√9+α2+5 The sum S is minimum when α=0 because √16+α2 and √9+α2 are minimum when α=0 ∵‌‌sec0=1