Notes about diagonal
#Formula for total number of diagonal of any regular polygon = n(n-3)/2 here n is number sides
Number of diagonal can be drawn from any vertex = n-3


#length of diagonal of a square= s√2 here 's' is length of side

#length of Main diagonal of a cube= s√3
however, length of "face" diagonal of a cube = s√2


# length of diagonal of a rectangle = √(a^2+b^2) , here a & b are sides of rectangle
# length of diagonal of a Solid rectangle = √(a^2+b^2+c^2) ,here a,b & c are sides of solid rectangle