Theorem of transversal segments
Diagram
$$\frac{AD}{BC}=\frac{XA}{XB}=\frac{XD}{XC}$$
the ratio is the scale factor of central similitude
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Diagram
$$\frac{AD}{BC}=\frac{XA}{XB}=\frac{XD}{XC}$$
the ratio is the scale factor of central similitude