Elementary Geometry for College Students (5th Edition)

$\alpha\approx48^{\circ}$ $\beta\approx42^{\circ}$
$\sin\beta=\frac{2x}{3x}=\frac{2}{3}$ $\beta=\sin^{-1}\frac{2}{3}$ $\beta\approx42^{\circ}$ Sum of interior angles of a triangle $= 180^{\circ}$ $90^{\circ} + \alpha + \beta = 180^{\circ}$ $90^{\circ} + \alpha + 42^{\circ} \approx 180^{\circ}$ $\alpha\approx48^{\circ}$