## helpplease1 Group Title Determine the general formula(s) for the solution. Then, determine the specific solutions on the interval [0,2pi). 2cos^2(theta)-3cos(theta)+1=0 one year ago one year ago

1. looser66 Group Title

still need help?

2. helpplease1 Group Title

yes i do :(

3. looser66 Group Title

let cos$$\theta$$= x, you have the form of $$2x^2-3x+1=0$$ solve for x as a quadratic equation, then plulg back to x = cos $$\theta$$ to solve for $$\theta$$

4. helpplease1 Group Title

thank you! but i mistyped the question it is actually plus 3, not 1. :( so would the quadratic equation be $2x ^{2}-3x+3$?

5. helpplease1 Group Title

i cannot figure out how to factor that

6. looser66 Group Title

which class are you in? do you know Euler's formula for complex number?

7. helpplease1 Group Title

i am just in a college trig class. 1316. we have not gotten to euler's formula thus far

8. helpplease1 Group Title

this is the actual problem $2\sin ^{2}\Theta-3\cos \Theta=-3$

9. looser66 Group Title

hey, it totally different,!! heehe , let see. 2 sin^2 = 2 - 2cos^2 therefore, 2-2cos^2 -3 cos +3 =0 2cos^2 +3 cos -5 =0, can solve it now

10. looser66 Group Title

you should post the original one, friend.

11. looser66 Group Title

you really scared me!! I thought I met a Ph.D student.

12. helpplease1 Group Title

lol i know i got it confused with another problem. I was really good at algebra but this stuff is just killing me...

13. helpplease1 Group Title

hahaha no ph.d student here

14. looser66 Group Title

so? everything is quite simple, right?

15. helpplease1 Group Title

so i have $2x ^{2}+3x-5=0$ and now factor? im sorry this class has confused me so much

16. looser66 Group Title

if you know how to factor, do it. if not, use discriminant. Either way is ok.

17. helpplease1 Group Title

x=-5/2 and x=1?

18. looser66 Group Title

yes, and reject -5/2, out of interval

19. helpplease1 Group Title

okay. so: cos(theta)=1? how do i make the general formula in form of of: _+_k

20. looser66 Group Title

not finish yet, cos $$\theta$$ =1 $$\rightarrow \theta$$ = 0 + 2k$$\pi$$ that 's the general formula solution for you

21. helpplease1 Group Title

so the only solution is 0? because subbing 1 for k would make 2pi which would not be included in the interval?

22. looser66 Group Title

yes, you are right. general form is 2kpi, specific solution in the interval is 0 Medal for a good student

23. helpplease1 Group Title

oh my gosh thank you so much for your help!

24. looser66 Group Title

do I help? No! just you work on it, I did nothing. hehee

25. helpplease1 Group Title

:) :)