Now, since \(0 < x < \frac\pi2\), \(u = \sin x + \cos x = \sqrt2 \sin\left(x + \frac\pi4\right)\), so \(u \in (1, \sqrt2]\) (maximum \(\sqrt2\) at \(x = \frac\pi4\)). - AMAZONAWS 📅 March 6, 2026 👤 scraface Mar 06, 2026