I have got a bunch of trig equations to solve for tomorrow, and got stuck on this one.
Solve for $\theta$:
$$3 - 2 \cos \theta - 4 \sin \theta - \cos 2\theta + \sin 2\theta = 0$$
I tried using the addition formula, product-to-sum formula, double angle formula and just brute force by expanding all terms on this, but couldn't get it.
I am not supposed to use inverse functions or a calculator to solve this.
Tried using Wolfram|Alpha's step by step function on this, but it couldn't explain things.