Quandaries and Queries
  


Name: laura

Who is asking: Other
Level: All

Question:
is there a way to establish, if a given point at coordinates (x,y) is within an area defined by three other sets of coordinates forming a triangle ABC?

is T(x,y) within triangle A(x,y)B(x,y)C(x,y)

sorry for my lack of notational knowledge in expressing this problem



Hi Laura,

Solve for the unknowns u, v, w in the 3 by 3 system:

uA+ vB + wC = P
u + v + w = 1 for its unique solution. P is inside triangle ABC if and only if u, v, w are all positive. (There might be a 4 by 4 determinant that provides the same information, but I've not thought about it.)

Chris


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