x1+x2=2l,y1+y2=0,z1+z2=0 x2+x3=0,y2+y3=2m,z2+z3=0 ‌ and ‌‌‌x1+x3=0,y1+y3=0,z1+z3=2n On solving, we get ‌‌‌x1=l,x2=l,x3=−l, ‌‌‌y1=−m,y2=m,y3=m ‌‌ and ‌‌‌z1=n,z2=−n,z3=n ‌∴‌ Coordinates are ‌A(l,−m,n),B(l,m,−n) ‌‌ and ‌C(−l,m,n) ‌∴‌‌‌
