$‎‎\sigma(x)‎$ ‎‎‎‎is ‎contained ‎in ‎the ‎imaginary ‎axis ‎of ‎the ‎complex ‎plane

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$‎A$ ‎is a‎ ‎C*-algebra ‎and ‎‎$‎x‎\in A‎$ ‎satisfies ‎‎$‎x‎^*=-x‎$.‎I want to show that ‎‎$‎‎\sigma(x)‎$ ‎‎‎‎is ‎contained ‎in ‎the ‎imaginary ‎axis ‎of ‎the ‎complex ‎plane.How i prove it?

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If you're looking for a proof: $ix$ is self-adjoint by your assumption $x^* = -x$. So $\sigma(ix) = i\cdot \sigma(x)$ lies on the real line.