prove that any two edges in a regular tetrahedron are perpendicular.

Dear jimmy singh

her O is origin

OA=OB=OC=AB=BC=CA

Now AB=BC=CA

|AB|²=|BC|²=|CA|²

|b-a|² =|c-a|²=|a-c|²

here a,b,c are position vector of A,B,C

|a|² +|b|² -2a.b =|b|² +|c|² -2c.b=|a|² +|c|² -2a.c

or a.b=b.c=c.a

or a.b=b.c

or  b.(a-c)=0

OB.AC=0

OB is perpendicular to AC

similerly for others