Two points and share the same –coordinate

MATHEMATICS · Subjective · CBSE · Mathematics · Introduction to Three-Dimensional Geometry · Introduction to Three-Dimensional Geometry

Problem

Two points

P(x_1,y_1,z)

and

Q(x_2,y_2,z)

share the same

z

–coordinate. What expression gives the distance

PQ

? Briefly justify why this simplification is valid.