## anonymous 3 years ago cos θ = − root2 /2

1. anonymous

how can you get rid of the cosine?

2. anonymous

arc cos?

3. anonymous

yep

4. anonymous

do you know the unit circle?

5. anonymous

yup

6. anonymous

okay, so where is cos(θ) = -sqrt(2/2) ?

7. anonymous

3pi/4

8. anonymous

Yes.. correct.

9. hartnn

10. hartnn

now do u need general solution or within the range 0 to 2pi ?

11. anonymous

these are the directionsSolve the given equation. (Enter your answers as a comma-separated list. Let k be any integer. Round terms to two decimal places where appropriate.)

12. hartnn

means genearalized solution, can u generalize this ?

13. anonymous

5pi/4 ,-5pi/4,3pi/4,-3pi/4

14. anonymous

There is an infinite amount of solutions, you need to write it in a way to GENERALIZE the solution.

15. hartnn

so let me generalize it. cos function is periodic with 2pi. so values repeat after every 2pi*k here, $$\theta =\pm(3\pi/4+2\pi k),\pm(5\pi/4+2\pi k)$$

16. anonymous

ohh i see but why do u add the 2pik at the end ? because it is a periodic function?

17. hartnn

yes, as i said cos function is periodic with 2pi. so if a is solution, so is a+2pi, a-2pi,a+4pi,a-4pi, and so on

18. anonymous

ohh i see i missed this whole lesson on this section and i dont know any of it