Solving Trigonometric Equations in Context Practice Test

The temperature (in °C) during a day is modeled by $T(t)=10\cos\left(\frac{\pi t}{12}\right)+20$, where $t$ is hours after midnight. Based on the model, when is the temperature $15^\circ\text{C}$ during the first 24 hours ($0\le t<24$)?

A rotating beacon’s brightness at a sensor is modeled by $B(t)=5\cos(2t)+10$, where $t$ is in seconds and $0\le t\le 2\pi$. Using the model, solve $B(t)=15$ for $t$ in the given interval.