SOLUTION: How can you determine if two lines are perpendicular? now i understand that they are perpendicular when the intersecting lines create a 90 degree angle but how do i explain that m

Question 151154: How can you determine if two lines are
perpendicular? now i understand that they are perpendicular when the intersecting lines create a 90 degree angle but how do i explain that more in depth in about 50 words?
Answer by nabla(475) (Show Source): You can put this solution on YOUR website!
Orthogonality is a generalization of perpendicularity. It is that which I will address. Two lines or vectors are orthogonal if and only if their slopes are negative reciprocals of each other. I will give you a general case in order to explain further:
Consider two lines:
y=mx+b
y=nx+c
Note, first, that b and c are irrelevant in determining parallelism, orthogonality, or skewness (neither parallel nor orthogonal, this applies in three dimensions). So, m and x are all we are worried about in determining which these two lines classify as.
If m=n, mx=mx, and we see that the lines share the SAME growth rate. They are parallel.
On the other hand, if we think about it, what do we want to happen to the growth rate in order for such lines to be orthogonal? First, we want the negative of the former, and we want it to grow at an inverse ratio. So, we want:
m=-1/n.

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