Chapter 6 - Trigonometric Functions - 6.2 Trigonometric Functions: Unit Circle Approach - 6.2 Assess Your Understanding - Page 380: 111

$\dfrac{\sqrt3}{2}$

RECALL: $(f \circ h)(x)=f\left(h(x)\right)$ Use the rule above to obtain: $\left(f\circ h\right)\left(\dfrac{\pi}{6}\right)=f\left(h\left(\dfrac{\pi}{6}\right)\right)=f\left(2\cdot\dfrac{\pi}{6}\right)=f\left(\dfrac{\pi}{3}\right)=\sin{\left(\dfrac{\pi}{3}\right)}=\dfrac{\sqrt3}{2}$