Chapter 9 - Trigonometric Identities, Models, and Complex Numbers - 9.1 Trigonometric Equations - Exercises and Problems for Section 9.1 - Exercises and Problems - Page 357: 6

$$θ=\frac{0.9272 }{3}, \frac{\pi -0.927}{3}$$

Solving the equation using inverse trigonometric functions, we find: $$5\sin \left(3θ\right)=4,\:0\le \:θ\le \frac{\pi }{2} \\ \sin \left(3θ\right)=\frac{4}{5} \\ θ=\frac{0.9272 }{3}, \frac{\pi -0.927}{3}$$