Posted by Diana on Thursday, June 17, 2010 at 10:29pm.
How can you determine if two lines are perpendicular?

Math  Reiny, Thursday, June 17, 2010 at 10:47pm
find their slopes.
If the are the opposite reciprocals of each other, they are perpendicular.
or
if their product is 1 they are perpendicular. 
Math  Diana, Thursday, June 17, 2010 at 10:50pm
thank you, But what if the product is something other than 1 Could it still be perpendicular? Why or Why not?

Math  Reiny, Thursday, June 17, 2010 at 11:12pm
nope, if the product is not 1, they are not perpendicular
If the slopes are opposite reciprocals, their product will always be 1. So that is the basic condition.
e.g. slope of first = 4/5
slope of second = 5/4
(4/5)(5/4) = 1 
Math  Diana, Thursday, June 17, 2010 at 11:39pm
Thank you!