How do you solve for cos2x = 2 cosx sinx?

[Maria]

I have on stupid question left:
Why do I get 4 angles instead og just 2?
Is it because tan =1?

 

[arildno]

You get 4 distinct angles because you must solve tan(2x)=1 rather than tan(x)=1
If for example, you were to solve tan(4x)=1, you would have even more distinct solutions
(You could work out how many for yourself)

 

[Maria]

thanks a lot for answering all my stupid questions...