Modeling with Trigonometric Functions · Exercise 44

Create a function modeling the described behavior. Then, calculate the desired result using a calculator.

A spring attached to a ceiling is pulled down 21 cm from equilibrium and released. After 6 seconds, the amplitude has decreased to 4 cm. The spring oscillates 20 times each second. Find when the spring first comes between $-0.1$ and $0.1\text{cm},$ effectively at rest.

Its source prints no answer for this problem, so there's nothing to check against.

OpenStax, Precalculus 2e · §7.6 Modeling with Trigonometric Functions · Exercise 44