the equation of the plane is

. To determine the coefficients

let

be the value of

for one of the four known points

. For example,

is the

value for the point

Then set

,

and

For the fifth point

,

Since 3 points determine a plane, the fourth known point should satisfy

The equation of a plane is

. To determine the coefficients

let

be the value of

for one of the four known points

. For example,

is the

value for the point

Now let

denote the fifth point. Take the first triangle to be (0,0), (64,0) and (0,64). The fifth point is in this triangle if

Then set

,

and

For the fifth point,

The second triangle is (64,64), (64,0) and (0,64). The fifth point is in this triangle if

Then set

,

and

For the fifth point,