## hawkfalcon What is x in this equation? one year ago one year ago

1. hawkfalcon

$\cos^2x +3cosx+2 = 0$

2. Mimi_x3

u = cosx

3. hawkfalcon

Oh then its just a quadratic :O

4. hawkfalcon

:P What happens to the cos though? Do it after?

5. Mimi_x3

u^2 + 3u + 2 = 0 solve for u then later sub it back in btw is it only me that latex is not working?

6. hawkfalcon

Okay, thank you. I think its just you:O

7. Mimi_x3

np

8. hawkfalcon

I can't believe I didn't see it was just a simple quadratic *.*

9. Mimi_x3

well using a substitution is easier; at times when you see like the x squared; there is a high chance that its a quadratic. so use a substitution.

10. hawkfalcon

Alright! Thank you so much:D