Chapter 2 - Acute Angles and Right Triangles - Section 2.1 Trigonometric Functions of Acute Angles - 2.1 Exercises - Page 53: 77

$\theta = 60 ^{\circ}$

1.$x=1$ ; $y=1.73\approx \sqrt 3$ 2.$r=\sqrt {(1)^{2}+(\sqrt 3)^{2}} = \sqrt 4 = 2$ 3. $\sin\theta = \frac{y}{r}=\frac{\sqrt 3}{2}$ $\sin^{-1} \frac{\sqrt 3}{2}=60^{\circ}$ $\theta = 60^{\circ}$