Question 965883: Use techniques of Analytic Geomatry to prove that the slope of one diagonal of a rectangle is the negative of the slope of another diagonal
Answer by Fombitz(32388) (Show Source):
You can put this solution on YOUR website! Let the rectangle have length a and width b.
One vertex is at ( , ).
One at ( , ).
One at ( , ).
One at ( , ).
The two points that join one diagonal are ( , ) and ( , .
The slope is,

The two points that join the other diagonal are ( , ) and ( , ).
That slope is,

.
.
So,
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