# Condition for two line to be coplanar

I want to know what is the condition for two lines to be coplanar . I searched it on internet.

I found that for coplanar the scalar product should be zero .

But I could not understand why it should be zero . And what are the three vectors whose scalar product is zero

• – user371838 Dec 25 '16 at 16:17
• @Rohan in that you have not mentioned about saclar product – Koolman Dec 25 '16 at 16:19
• In general we check for coplanarity like that. – user371838 Dec 25 '16 at 16:20
• @Rohan can you post an answer in detail explanation. – Koolman Dec 25 '16 at 16:25
• 3 vectors or 2 vectors? – Fawad Dec 25 '16 at 16:36

$$x=a+ut$$ $$y=b+vt$$ $$z=c+wt$$ where $(a,b,c)$ is a point of the line, $(u,v,w)$ the vector director and $t$ a parameter.