A simple proof of the elliptical range theorem

A simple proof of the elliptical range theorem
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by Chi-Kwong Li

Proc. Amer. Math. Soc. 124 (1996), 1985-1986

DOI: https://doi.org/10.1090/S0002-9939-96-03307-2

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A short proof is given of the elliptical range theorem concerning the numerical range of a $2\times 2$ complex matrix.

References

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