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The fact that the global scaling parameters of clusters of galaxies are controlled by the virial theorem is perhaps not surprising. Showing such a relation with optical data is difficult. With x-ray data it is straightforward. The x-ray surface brightness profile of 80 clusters of galaxies with known x-ray temperatures were measured using ellipse fitting techniques. There is a two dimensional surface in the cluster temperature, surface brightness, and effective radius three space; a principal component analysis shows that ellipticity, $a4/a$ and other shape parameters are uncorrelated with this plane. The effective radius of the cluster may be predicted using $T_x$ and SB$_x$ with rms residuals of $10\%$. The relationship found is that expected from the virial theorem and bremsstrahlung.
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