A ladder 10 meters long leans against a wall, forming a 75° angle with the ground. How high up the wall does the ladder reach? (Round to nearest tenth)

📌 Solution: Let $ \alpha = \sqrt{1 + i} $, $ \beta = \sqrt{1 - i} $. The conjugate pairs $ \alpha $ and $ -\alpha $, $ \beta $ and $ -\beta $ must both be roots for real coefficients, but since the polynomial is monic of degree 2 and has only these two specified roots, we must consider symmetry. Instead, compute the sum and product. Note $ (1 + i) + (1 - i) = 2 $, and $ (1 + i)(1 - i) = 1 + 1 = 2 $. Let $ z^2 - ( \alpha + \beta )z + \alpha\beta $. But observing that $ \alpha\beta = \sqrt{(1+i)(1-i)} = \sqrt{2} $. Also, $ \alpha^2 + \beta^2 = 2 $, and $ \alpha^2\beta^2 = 2 $. Let $ s = \alpha + \beta $. Then $ s^2 = \alpha^2 + \beta^2 + 2\alpha\beta = 2 + 2\sqrt{2} $. But to find a real polynomial, consider that $ \alpha = \sqrt{1+i} $, and $ \sqrt{1+i} = \sqrt{\sqrt{2}} e^{i\pi/8} = 2^{1/4} (\cos \frac{\pi}{8} + i\sin \frac{\pi}{8}) $. However, instead of direct polar form, consider squaring the sum. Alternatively, note that $ \alpha $ and $ \beta $ are conjugate-like in structure. But realize: $ \sqrt{1+i} $ and $ \sqrt{1-i} $ are not conjugates, but if we form a polynomial with both, and require real coefficients, then the minimal monic polynomial must have roots $ \sqrt{1+i}, -\sqrt{1+i}, \sqrt{1-i}, -\sqrt{1-i} $ unless paired. But the problem says "roots at" these two, so assume $ \alpha = \sqrt{1+i} $, $ \beta = \sqrt{1-i} $, and for real coefficients, must include $ -\alpha, -\beta $, but that gives four roots. Therefore, likely the polynomial has roots $ \sqrt{1+i} $ and $ \sqrt{1-i} $, and since coefficients are real, it must be invariant under conjugation. But $ \overline{\sqrt{1+i}} = \sqrt{1 - i} = \beta $, so if $ \alpha = \sqrt{1+i} $, then $ \overline{\alpha} = \beta $. Thus, the roots are $ \alpha $ and $ \overline{\alpha} $, so the monic quadratic is $ (z - \alpha)(z - \overline{\alpha}) = z^2 - 2\operatorname{Re}(\alpha) z + |\alpha|^2 $. Now $ \alpha^2 = 1+i $, so $ |\alpha|^2 = |\alpha^2| = |1+i| = \sqrt{2} $. Also, $ 2\operatorname{Re}(\alpha) = \alpha + \overline{\alpha} $. But $ (\alpha + \overline{\alpha})^2 = \alpha^2 + 2|\alpha|^2 + \overline{\alpha}^2 $? Wait: better: $ \operatorname{Re}(\alpha) = \frac{ \alpha + \overline{\alpha} }{2} $. From $ \alpha^2 = 1+i $, take real part: $ \operatorname{Re}(\alpha^2) = \operatorname{Re}(1+i) = 1 = |\alpha|^2 \cos(2\theta) $, $ \operatorname{Im}(\alpha^2) = \sin(2\theta) = 1 $. So $ \cos(2\theta) = 1/\sqrt{2} $, $ \sin(2\theta) = 1/\sqrt{2} $, so $ 2\theta = \pi/4 $, $ \theta = \pi/8 $. Then $ \operatorname{Re}(\alpha) = |\alpha| \cos\theta = \sqrt{2} \cos(\pi/8) $. But $ \cos(\pi/8) = \sqrt{2 + \sqrt{2}} / 2 $, so $ \operatorname{Re}(\alpha) = \sqrt{2} \cdot \frac{ \sqrt{2 + \sqrt{2}} }{2} = \frac{ \sqrt{2} \sqrt{2 + \sqrt{2}} }{2} $. This is messy. Instead, use identity: $ \alpha^2 = 1+i $, so $ \alpha^4 = (1+i)^2 = 2i $. But for the polynomial $ (z - \alpha)(z - \beta) = z^2 - (\alpha + \beta)z + \alpha\beta $. Note $ \alpha\beta = \sqrt{(1+i)(1-i)} = \sqrt{2} $. Now $ (\alpha + \beta)^2 = \alpha^2 + \beta^2 + 2\alpha\beta = (1+i) + (1-i) + 2\sqrt{2} = 2 + 2\sqrt{2} $. So $ \alpha + \beta = \sqrt{2 + 2\sqrt{2}} $? But this is not helpful. Note: $ \alpha $ and $ \beta $ satisfy a polynomial whose coefficients are symmetric. But recall: the minimal monic polynomial with real coefficients having $ \sqrt{1+i} $ as a root must also have $ -\sqrt{1+i} $, unless we accept complex coefficients, but we want real. So likely, the intended polynomial is formed by squaring: suppose $ z = \sqrt{1+i} $, then $ z^2 - 1 = i $, so $ (z^2 - 1)^2 = -1 $, so $ z^4 - 2z^2 + 1 = -1 \Rightarrow z^4 - 2z^2 + 2 = 0 $. But this has roots $ \pm\sqrt{1+i}, \pm\sqrt{1-i} $? Check: if $ z^2 = 1+i $, $ z^4 - 2z^2 + 2 = (1+i)^2 - 2(1+i) + 2 = 1+2i-1 -2 -2i + 2 = (0) + (2i - 2i) + (0) = 0? Wait: $ (1+i)^2 = 1 + 2i -1 = 2i $, then $ 2i - 2(1+i) + 2 = 2i -2 -2i + 2 = 0 $. Yes! So $ z^4 - 2z^2 + 2 = 0 $ has roots $ \pm\sqrt{1+i}, \pm\sqrt{1-i} $. But the problem wants a quadratic. However, if we take $ z = \sqrt{1+i} $ and $ -\sqrt{1-i} $, no. But notice: the root $ \sqrt{1+i} $, and its negative is also a root if polynomial is even, but $ f(-z) = f(z) $ only if symmetric. But $ f(z) = z^2 - 1 - i $ has $ \sqrt{1+i} $, but not symmetric. The minimal real-coefficient polynomial with $ \sqrt{1+i} $ as root is degree 4, but the problem likely intends the monic quadratic formed by $ \sqrt{1+i} $ and its conjugate $ \sqrt{1-i} $, even though it doesn't have real coefficients unless paired. But $ \sqrt{1-i} $ is not $ -\overline{\sqrt{1+i}} $. Let $ \alpha = \sqrt{1+i} $, $ \overline{\alpha} = \sqrt{1-i} $ since $ \overline{\sqrt{1+i}} = \sqrt{1-\overline{i}} = \sqrt{1-i} $. Yes! Complex conjugation commutes with square root? Only if domain is fixed. But $ \overline{\sqrt{z}} = \sqrt{\overline{z}} $ for $ \overline{z} $ in domain of definition. Assuming $ \sqrt{1+i} $ is taken with positive real part, then $ \overline{\sqrt{1+i}} = \sqrt{1-i} $. So the conjugate is $ \sqrt{1-i} = \overline{\alpha} $. So for a polynomial with real coefficients, if $ \alpha $ is a root, so is $ \overline{\alpha} $. So the roots are $ \sqrt{1+i} $ and $ \sqrt{1-i} = \overline{\sqrt{1+i}} $. Therefore, the monic quadratic is $ (z - \sqrt{1+i})(z - \overline{\sqrt{1+i}}) = z^2 - 2\operatorname{Re}(\sqrt{1+i}) z + |\sqrt{1+i}|^2 $. Now $ |\sqrt{1+i}|^2 = |\alpha|^2 = |1+i| = \sqrt{2} $? No: $ |\alpha|^2 = |\alpha^2| = |1+i| = \sqrt{2} $? No: $ |\alpha|^2 = | \alpha^2 |^{1} $? No: $ |\alpha^2| = |\alpha|^2 $, and $ \alpha^2 = 1+i $, so $ |\alpha|^2 = |1+i| = \sqrt{1^2 + 1^2} = \sqrt{2} $. Yes. And $ \operatorname{Re}(\alpha) = \frac{ \alpha + \overline{\alpha} }{2} $. From $ \alpha^2 = 1+i $, take modulus: $ |\alpha|^4 = |1+i|^2 = 2 $, so $ (|\alpha|^2)^2 = 2 $, thus $ |\alpha|^4 = 2 $, so $ |\alpha|^2 = \sqrt{2} $ (since magnitude positive). So $ \operatorname{Re}(\alpha) = \frac{ \alpha + \overline{\alpha} }{2} $. But $ (\alpha + \overline{\alpha})^2 = \alpha^2 + 2|\alpha|^2 + \overline{\alpha}^2 $? No: $ \overline{\alpha}^2 = \overline{\alpha^2} = \overline{1+i} = 1-i $. So $ (\alpha + \overline{\alpha})^2 = \alpha^2 + 2\alpha\overline{\alpha} + \overline{\alpha}^2 = (1+i) + (1-i) + 2|\alpha|^2 = 2 + 2\sqrt{2} $. Therefore, $ \alpha + \overline{\alpha} = \sqrt{2 + 2\sqrt{2}} $. So the quadratic is $ z^2 - \sqrt{2 + 2\sqrt{2}} \, z + \sqrt{2} $. But this is not nice. Wait — there's a better way: note that $ \sqrt{1+i} = \frac{\sqrt{2}}{2}(1+i)^{1/2} $, but perhaps the intended answer is to use the identity: the polynomial whose roots are $ \sqrt{1\pm i} $ is $ z^4 - 2z^2 + 2 = 0 $, but we want quadratic. But the only monic quadratic with real coefficients having $ \sqrt{1+i} $ as a root must also have $ -\sqrt{1+i} $, $ \overline{\sqrt{1+i}} $, $ -\overline{\sqrt{1+i}} $, and if it's degree 4, but the problem asks for quadratic. Unless $ \sqrt{1+i} $ is such that its minimal polynomial is quadratic, but it's not, as $ [\mathbb{Q}(\sqrt{1+i}):\mathbb{Q}] = 4 $. But perhaps in the context, they want $ (z - \sqrt{1+i})(z - \sqrt{1-i}) $, but again not real. After reconsideration, the intended solution likely assumes that the conjugate is included, and the polynomial is $ z^2 - 2\cos(\pi/8)\sqrt{2} z + \sqrt{2} $, but that's not nice. Alternatively, recognize that $ 1+i = \sqrt{2} e^{i\pi/4} $, so $ \sqrt{1+i}

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