Best way to solve: cos 2 theta + 3 sin theta = 2 ?
1 Answer
Explanation:
First we have to use the Double Angle Theorem for cosine:
Then replacing this into our equation:
Then combining like-terms:
Now we can see that this is simply a quadratic in disguise, to see this easier you can replace
So now we have our two zeros of the equation:
Simplifying this we get:
But we cannot exclude all the others solutions of the sinusoidal function, so we add by its period times
Thus we get the answer: