Answer
$$θ=2.01 ,\:θ=4.28$$
Work Step by Step
Solving the equation using inverse trigonometric functions, we find:
$$\cos \left(θ\right)=-0.4226,\:0\le \:θ\le \frac{3\pi }{2} \\ θ=\arccos \left(-0.4226\right)+2\pi n,\:θ=-\arccos \left(-0.4226\right)+2\pi n \\ θ=2.01 ,\:θ=4.28$$