<PRE><B>Question 870653</B>
Show that the triangle formed by the points (-2,5), (1,3) and (5,9) is right angled.
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One way is to use the distance formula to see if the Pythagorean theorem holds for the lengths of the 3 sides:
A=(-2,5)
B=(1,3)
C=(5,9)
AB = sqrt(3^2+2^2) = sqrt(13) = a
BC = sqrt(4^2+6^2) = sqrt(52) = b
AC = sqrt(7^2+4^2) = sqrt(65) = c
a^2 + b^2 = 13 + 52 = 65 = c^2
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