Question 806276: I am looking for a formula that will show if coordinates are within or outside a set parallelogram.
Answer by solver91311(24713)   (Show Source):
You can put this solution on YOUR website!
Assume the coordinates of the four vertices are given and that they are ) , ) , ) , and ) . Since coordinate rotation and the labeling of the vertices is arbitrary, we can assume without loss of generality that the following inequalities hold:
and
Now write the following four inequalities using your given coordinates:
\left(x\ -\ x_1\right)\ +\ y_1)
\left(x\ -\ x_2\right)\ +\ y_2)
\left(x\ -\ x_4\right)\ +\ y_4)
\left(x\ -\ x_1\right)\ +\ y_1)
If a point on a side of the parallelogram is considered "in" the parallelogram, then change the inequality operators from strictly less than/greater than, to  or 
Then if the coordinates of a point satisfy ALL FOUR inequalities, the point is in the parabola, otherwise it is not.
John
Egw to Beta kai to Sigma
My calculator said it, I believe it, that settles it
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