Question

plssssssssssss help.
(i)Expand (lxm).(lxn). Hence prove that the acute angle between two faces of a regular tetrahedron is cos^-1(1/3).
(ii)Expand (lxm)x(lxn), and show its direction depends on whether the triad l,m,n is right- handed or left-handed. Hence prove that the volume of a regular tetrahedron is ((sqrt2)a^3)/12, where a is the length of each edge.

Answer 1

aaha

Answer 2

this is vectors

Answer 3

gottit