Mathematics - Inverse Trigonometric Functions Question with Solution | TestHub

At x=$\pi /4$, 2${\tan }^{-1}(1/\sqrt{2})={\tan }^{-1}(2\sqrt{2})$, using tan double-angle within (-$\pi /2,\pi /2$). Other solutions occur modulo π, so the stem says which listed value rather than implying uniqueness.