Showing Collinearity: Methods & Geometric Shapes

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This discussion focuses on methods to determine the collinearity of three points in a geometric context. Key techniques include using the wedge product of vectors PQ and PR, which confirms collinearity if the result is zero, indicating parallel vectors. Additionally, calculating the distances between the points—d(P,Q), d(P,R), and d(Q,R)—can also establish collinearity if the sum of the two smaller distances equals the third distance. These methods provide both standard and alternative approaches to assessing collinearity.

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dtl42
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What methods are there to show that three points are, or aren't collinear?

I know the standard, check the slopes stuff, but what other ways are there, I think there are some more obscure methods for geometric shapes right?

Thanks very much.
 
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if the points are P, Q and R, you can always wedge (i.e. take the vector product of) the vectors PQ and PR. The points will be colinear if and only if the wedge product is zero (i.e. the PQ and QR are parallel).
 
A straight line is the shortest distance between points. Calculate d(P,Q), d(P,R), d(Q,R), P, Q, and R are collinear if the sum of the two smaller distances is equal to the third distance.
 

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