## 3psilon 3 years ago sinx + 2cosx = 0 where 0<=x<=2pi, what can x be equal to

1. anonymous

sinx=-2cosx sinx/cosx=-2 tanx=-2 Whatever x that fits tanx=-2

2. 3psilon

so I did $\tan^{-1}(-2)$ and I got -1.107 which isn't correct

3. 3psilon

@nightwill

4. anonymous

x has to be between 0 and 2pi, so -1.107 won't work.

5. anonymous

6. 3psilon

Why did you add pi ?

7. 3psilon

I'm trying to refresh on trig

8. anonymous

I added pi so that it fits in the domain. tan x has a period of pi, so tan x = tan (x+pi) Therefore, $\tan(tan^{-1}-2)=tan(\pi+tan^{-1}-2)$