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#### ghostfirefox

##### New member

- Nov 13, 2019

- 14

- Thread starter ghostfirefox
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- Nov 13, 2019

- 14

Have you made a sketch?

- Jan 29, 2012

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- #4

- Nov 13, 2019

- 14

I have a question how you calculated the x coordinate of point D?You titled this "Analytic geometry proof ..." so I would set up a coordinate system so that the origin is at the vertex "B" of the triangle and the x-axis lies along on side BC. Then B= (0, 0), A= (x, y), and C= (z, 0) for some numbers x, y, and z. Since D lies on AC such that "|AD|:|DC|= 1:2",D= ((2x+ z)/3, 2y/3). Now, what are the vectors [tex]\vec{BA}[/tex], [tex]\vec{BC}[/tex]. and [tex]\vec{BD}[/tex]?

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