A community for students.
Here's the question you clicked on:
 0 viewing
anonymous
 3 years ago
Solve 4sin^2x + (4√2)cos x  6 = 0 for 0 < x < 2π
a. 3π/4, 7π/4
b. π/4, 7π/4
c. π/4, 5π/4
d. 3π/4, 5π/4
anonymous
 3 years ago
Solve 4sin^2x + (4√2)cos x  6 = 0 for 0 < x < 2π a. 3π/4, 7π/4 b. π/4, 7π/4 c. π/4, 5π/4 d. 3π/4, 5π/4

This Question is Closed

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0okay tell me what you know first?

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0i don't even know way to start. trig functions really confuse me

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0okay let me ask you do you know the unit circle?

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0recall the untit circle and where sin is and so forth

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0now let's look at the problem e 4sin^2x + (4√2)cos x  6 = 0 for 0 < x < 2π tell what the 0>x>2 pi means?

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0that is the limit or where this anser would fall on the circle

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0okay now to slove the problem 4sin^2x what can be done here?

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1@godorovg If you're stuck, let me know :3 I can provide some assistance. I don't wanna step on your toes if you've got this though :)

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0yeah I could use some help here I am tying to think how to do this in a simple way can you retrice me?

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1\[\large \sin^2 x + \cos^2 x = 1\]\[\large \sin^2 x = 1\cos^2 x\] Using this second identity, we can write the entire equation in terms of cosines, and then treat it as a quadratic equation from there. Using the quadratic equation if necessary :D

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1Quadratic formula* blah i always mix those two up.. i forget which is which :3

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0if you look at answers I think it is way first way

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1Oh an alternative, possibly easier method, since this is multiple choice, might be to just plug in your values given in A and see if it equals 0 or not. Just process of elimination :)

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1Although on a test that might not work so well :3 so you might wanna learn the method hehe

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0this isn't me asking this question I was trying to help only

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1I know, i was talking to kenney ^^ my bad

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0okay sorry I thought you were speaking to me

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1Using this identity:\[\large \sin^2 x = (1\cos^2 x)\] Our equation becomes:\[\large 4\sin^2 x +4\sqrt2 \cos x  6 = 0\]\[\large 4(1\cos^2 x) +4\sqrt2 \cos x  6 = 0\]

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1Understand what we did for the first step kenney? :O it's a little tricky, we're taking advantage of a trig identity.

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1kenney too quiet _ hehe

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0sorry haha just trying to read all this and take it in

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0if we go too fast for you tell us okay

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0answer choices are: a. 3π/4, 7π/4 b. π/4, 7π/4 c. π/4, 5π/4 d. 3π/4, 5π/4

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0if take the unit circle and find these than you can slove this that way

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0how will locating on the unit circle help?

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0if you know sin and cos and sec it's in you can use these values and use them

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1\[\large 4(1\cos^2 x) +4\sqrt2 \cos x  6 = 0\] Distributing the 4 gives us:\[\large 44\cos^2 x +4\sqrt2 \cos x  6 = 0\]\[\large 4\cos^2 x +4\sqrt2 \cos x  2 = 0\] Dividing both sides by 1 gives us:\[\large 4\cos^2 x4\sqrt2 \cos x +2 = 0\] From here, we can think of cosx as something simple like U and it might be easier for you to solve it from there, using the quadratic formula. \[\large 4u^24\sqrt2u+2=0\] \[\large u=\frac{ b \pm \sqrt{b^24ac} }{ 2a }\]

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1These are some of the steps you would take to solve this. It's a little tricky, it touches on trig AND some algebra stuff.. take a look at steps and maybe ask questions if you're confused by anything :D

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0wait I am trying but failing to see something here??

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1I'm not exactly sure where you are with this material, so I figure I'd at least show you how to get the solution and maybe you can work though it at your own pace.

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0sorry i'm lost..how will the quadratic formula help?

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1maybe it was unnecessary to change to U, I hope that didn't confuse you. U=cosx in this case. So we're solving for cosx. The quadratic formula will end up giving us a special angle.

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1A value that corresponds to one of the special angles i mean*

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1\[\large \cos x = \frac{ 4\sqrt2 \pm \sqrt{(4\sqrt2)^24(4)(2)} }{ 2(4) }\] \[\large \cos x = \frac{ 4\sqrt2 \pm \sqrt{3232} }{ 8 }\]\[\large \cos x = \frac{\sqrt2}{2}\]

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1It's kinda tricky to get there, but see what we did? :O We got a nice number that refers back to one of our reference angles.

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0zep answers are these a. 3π/4, 7π/4 b. π/4, 7π/4 c. π/4, 5π/4 d. 3π/4, 5π/4 help me to see this??

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1So cos x is a POSITIVE sqrt(2)/2 at ... pi/4.. andddd... anyone remember the other one? :D

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0thanks!!!! you guys are awesome!!! :D

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0zep that was what I was doing with the unit circle.

zepdrix
 3 years ago
Best ResponseYou've already chosen the best response.1If there is a simpler way to get through this problem, then I apologize :D But this is how I remember doing it. As mentioned before, you can always try plugging your options into your initial equation and see which ones give you 0 :O

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0no I think thanks for the help zep I am sorry I guess I am still rusty llittle forgive me Kenndy

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0no worries..all help was appreciated!
Ask your own question
Sign UpFind more explanations on OpenStudy
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.