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eguruchela

List of formulas related to Analytic-geometry (Line in 2D)


Line forms

Slope y-intercept form:

y=mx+b

Two point form:

yy1=y2y1x2x1(xx1)

Point slope form:

yy1=m(xx1)

Intercept form:

xa+yb=1 , (a,b0)

Normal form:

xcosΘ+ysinΘ=p

Parametric form:

x=x1+tcosαy=y1+tsinα

Point direction form:

xx1A=yy1B

where (A,B) is the direction of the line and P1(x1,y1) lies on the line. General form:

Ax+By+C=0 , (A0 or B0)

Distance

The distance from Ax+By+C=0 to P1(x1,y1) is

d=|Ax1+By1+C|A2+B2

Concurrent lines

Three lines

A1x+B1y+C1=0A2x+B2y+C2=0A3x+B3y+C3=0

are concurrent if and only if:

|A1B1C1A2B2C2A3B3C3|=0

Line segment

A line segment P1P2 can be represented in parametric form by

x=x1+(x2x1)ty=y1+(y2y1)t0t1

Two line segments P1P2 and P3P4 intersect if any only if the

s=|x2x1y2y1x3x1y3y1||x2x1y2y1x3x4y3y4|  and  t=|x3x1y3y1x3x4y3y4||x2x1y2y1x3x4y3y4|
satisfy 0s1 and 0t1