Solve for $-\pi <\theta < \pi$: $$\tan\theta=\cos\theta$$
I can't get to the correct solution using the identities: $$\tan\theta=\frac{\sin\theta}{\cos\theta} \quad\text{and}\quad \sin^2\theta+\cos^2\theta=1$$
The answer I'm getting is
$$\sin\theta=-\frac12\pm\frac12 \sqrt{5}$$
giving: $0.62$ and $-1.62$.
The answers in the back of the book are $0.67$ and $2.48$.
Any hints much appreciated. Thanks!