## anonymous one year ago (cos Θ + cos Θ)^2 + (cos Θ + cos Θ)^2 answers are sin2 Θ 4 8 cos2 Θ

1. anonymous

2. Astrophysics

I just showed you this :\

3. Astrophysics

Someone else isn't going to get a different answer...they will tell you your options are wrong as well, we got $8 \cos^2(\theta)$

4. anonymous

yes but i was hoping someone cou;d help me answer it maybe theres a different way

5. Astrophysics

$(\cos(\theta)+\cos(\theta)^2 = (2\cos \theta)^2 = 4\cos^2(\theta)$ since both sides are same we have $4\cos^2(\theta)+4\cos^2(\theta) = 8\cos^2(\theta)$

6. Astrophysics

Your options don't make sense, either you just pick one at random or email your teacher

7. anonymous

okay i think im going to go with 8

8. Astrophysics

Post the full question

9. Astrophysics

Maybe you missed a detail

10. Astrophysics

Including everything

11. anonymous

12. Astrophysics

Yeah ok the options are wrong, go either 8 or cos^2theta I guess :\ make sure to tell your teacher

13. anonymous

tahts all it is

14. anonymous

do you mind helping w another

15. Astrophysics

sure

16. anonymous

what is the sine value of 5pi/3

17. anonymous

i know its equal to 300 degrees

18. anonymous

?

19. Astrophysics

$\sin(5 \pi/3)$ ok so we have this, the reference angle here is pi/3 what's the ratio of sin(theta)?

20. anonymous

im not sure

21. anonymous

im sorry im really bad at math i just know tis equal to 300 degrees

22. Astrophysics

SOH CAH TOA

23. Astrophysics

that ring a bell?

24. Astrophysics

$\sin( \theta) = \frac{ opposite }{ hypotenuse } = \frac{ x }{ r }$

25. anonymous

oh yeah

26. Astrophysics

|dw:1439605676428:dw| this is the pi/3 triangle, so far so good?

27. anonymous

yes

28. Astrophysics

Ok since we know it's 300 degrees we know it's in the fourth quadrant of unit circle right. So$y=-\sqrt{3}$and$r = 2$$\frac{ y }{ r } = \frac{ - \sqrt{3} }{ 2 }$ sorry I put x as opposite when it should be y/r and not x/r.

29. anonymous

okay

30. Astrophysics

So that's our exact value

31. anonymous

thank you so much

32. Astrophysics

Np