I solved 2 cos(2x)+3=2 using inverse and then solved the same equation using the double angle formula, why are the answers different? what is the correct method?

Question

anonymous · Answer

what is your answer when solving as usual?

anonymous · Answer

I get 60 and 120 when I use the inverse
but when I use the double angle formula I get 60 120 240 and 300

mertsj · Answer

$$\cos 2x=\frac{-1}{2}$$

mertsj · Answer

$$2x= \frac{2\pi}{3}, \frac{4\pi}{3} + 2\pi n$$

anonymous · Answer

that is what i got when i did the inverse

mertsj · Answer

$$x=\frac{\pi}{3}, \frac{2\pi}{3} + 2\pi n$$

mertsj · Answer

Which double angle formula did you use?

anonymous · Answer

i used 2cos^2(x) - 1 and then distributed and got two additional answers but I wanted only answers between 0 and 360 degrees

mertsj · Answer

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