# Thread: Definition of a plane using 3 points

1. ## Definition of a plane using 3 points

n = (p2-p1) x (p3-p2)

p1 =[0,1,1] p2 = [2,-1,2] p3 =[-3,1,0]

= [ 2,-2,1] x [-5,2,-2]

the answer is [2,-1,-6] but I cant see how to get could someone show me please?

2. Originally Posted by aoibha
n = (p2-p1) x (p3-p2)
p1 =[0,1,1] p2 = [2,-1,2] p3 =[-3,1,0]
= [ 2,-2,1] x [-5,2,-2]
the answer is [2,-1,-6] but I cant see how to get could someone show me please?
Frankly you notation is so poor as to make it impossible to follow.
If we have points then

Now take

The plane is

3. Is still dont see how to get [2,-1,-6]

4. Originally Posted by aoibha
Is still dont see how to get [2,-1,-6]
Do you know how to do a cross product?

5. Could you show me please?

6. the direction of the cross product is determined by the right-hand rule. Here is the angle between the two vectors.