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If \(z_1\) and \(z_2\) are the roots of the polynomial \(ax^2+bx+c\) with real coefficients and \(b^2<4ac\) prove that if \(z_1=\overline{z_{2}}\) then $$\arg\left(\frac{z_{1}}{z_{2}}\right)=2\arccos\left(\sqrt{\frac{b^2}{4ac}}\right)\,.$$