The three vectors 
, 
, and 
each terminate on the plane. We can get two vectors that lie on the plane itself (or rather, point in the same direction as vectors that do lie on the plane) by taking the vector difference of any two of these. For instance,
Then the cross product of these two results is normal to the plane:
Let 
be a point on the plane. Then the vector connecting to a known point on the plane, say (0, 0, 1), is orthogonal to the normal vector above, so that
which reduces to the equation of the plane,
Let 
. Then the volume of the region above 
and below the plane is
When angles and sides are all equal
If a 15 lbs dog eats................................17/8 cups of food
a 34 lbs dog will eat,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,? cups
(34 * 17/8)/15=(34*17)/(15*8)=289/15= 19 4/15 cups of food
