Is the condition m1*m2 =-1 always valid where m1,m2 are the slopes of perpendicular lines?because if we take the case of x-axis and y-axis (infinity *0 is never equal to -1)

Dear tarun,

That is a different thing axis are the basis on which whole geometry is based...

m1m2=-1 is always valid...

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Sagar Singh

B.Tech IIT Delhi

It is always vailed. x-axis and y-axis are to determine the directions and cartisions points. if we talk any line being perpendicular to x-axis like x=2 then what will be its slop that doen't make any sense thus i think you wold have understood the concept.