What algorithm or formula can it be ascertained whether the point between the parallel straight?

There are two parallel straight equations:
a_{1}x + b_{1}y + c_{1} = 0
a_{2}x + b_{2}y + c_{2} = 0.How to determine whether the P(x, y) point is between them?

For example, this is how:
Let
n
 the general vector normalized your direct,A1
andA2
 1st and 2nd straight points, respectivelyX
 Checkpoint. Calculate the scalary works(XA1, n)
and(XA2, n)
♪ The point lies inside if these works have the opposite sign.Not necessarily parallel direct and stupid corner, we' corner. two Normal vector
n1
andn2
♪ Then the following values should be established:isFirstDirectionPositive
 the sign of the polar work(XA1, n1)
(respectively, the result of the setting of the point in the first straight equation),isSecondDirectionPositive
 the sign of the polar work(XA2, n2)
(respectively, the result of the point set in the second straight equation) andisAngleBetweenNormalsAcute
 the sign of the polar work(n1, n2)
♪ You need a piece of work. All three The signs were positive.