Please tell me the formulae for the problems.?

Question

to find the length of a diagonal when dimensions of a cube or cuboid is given
to find the height of a triangle when area is given

Answer 1

for the first one:
x V 2 ("V" is the radical sign) , where "x" is the dimension of the cube

for the second:
A = (b+h)/2 , where "A" is area, "b"
is the bottom line of the triangle and "h" height

Answer 2

calculate diagonal of the base
use pisagor to find cube diagonal
it is d=sqrt(2a^2+a^2=
d=a . sqrt(3)

a is the length of a side


area=a*h/2

h=2*area/ a

a is the base