# Anne F

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### On This Day in Math - February 16

<b>Whenever you can, count.</b><p>~Sir Francis Galton<p>The 47th day of the year; 47 is a Thabit number, named after the Iraqi mathematician Thâbit ibn Kurrah …

By the construction, $AO=BO=CO=OX,$ giving four isosceles triangles $BOX,COX,AOC, AOB.$ For convenience let $\angle BAC=\alpha,$ $\angle AOY=\tau,$ …