LoseUrself2Dance Posted October 22, 2015 Share Posted October 22, 2015 (edited) SO DIFFERENTIATION OF TRIGONOMETRICAL FUNCTIONS (or something, I didn't learn this in English); this problem in particular: 4x(cos x - cos 2x) f(x) = ------------------------- sin x * cos 2x Anyone would like to lend a hand to find f'(x)? :D Edit: The answer I got waaaas: 4sin2x (cos x * cos 2x * sin x - x cos 2x *+ x cosx * sin 2x * sin x) + cos x * cos22x f'(x) = ---------------------------------------------------------------------------------------------------------------------------------- cos22x * sin2x THIS WAS WRONG. FINAL ANSWER BELOW But I have no answer sheet so I can't check the answer. Edit, my working: (not derived yet) 4x(cos x - cos 2x) f(x) = ------------------------- sin x * cos 2x 4x * cos x cos 2x = ----------------- - ------------- sin x * cos2x sin x * cos 2x 4x * cot x cos 2x = -------------- - ----------------- cos 2x sin x * cos 2x 4x * cot x 1 = -------------- - --------- cos 2x sin x 4x * cot x = -------------- - cosec x cos 2x (deriving now) (used quotient rule, but since there was 4x * cot x I had to use product rule within the quotient rule(?)) (4 cot x - 4x*cosec2x) * cos 2x - (4x * cot x)(-2sin2x) f'(x) = ----------------------------------------------------------------------------------- + cosec x * cot x (cos 2x)2 4 cot x * cos 2x - 4x*cosec2x * cos 2x + 4x*cot x * sin 2x 1 cos x = ------------------------------------------------------------------------------------- + ----- * -------- cos2x sin x sin x 4 cot x * cos 2x - 4x*cosec2x * cos 2x + 4x*cot x * sin 2x cos x = ------------------------------------------------------------------------------------- + --------- cos2x sin2x 4 cos x * cos 2x 4x * cos 2x 4x * cos x * sin 2x ---------------------- - --------------- + ------------------------ sin x sin2 sin x cos x = ------------------------------------------------------------------------- + -------- cos2x sin2x 4 cos x * cos 2x * sin x - 4x * cos 2x + 4x * cos x * sin 2x * sin x cos x = --------------------------------------------------------------------------------- + -------- sin2x * cos2x sin2 x 4 cos x * cos 2x * sin x - 4x * cos 2x + 4x * cos x * sin 2x * sin x + cos x * cos2x = ----------------------------------------------------------------------------------------------------------- sin2x * cos2x I THINK this is the final answer..? Good Lord that took a while Edited October 22, 2015 by LoseUrself2Dance Link to comment Share on other sites More sharing options...
Freelancer27 Posted October 22, 2015 Share Posted October 22, 2015 (edited) All right then. Never mind. Old post: Can't you derive Trigonometry yourself? Feels like you are asking assignment answers from the internet in the hopes someone would give you a wrong answer, without even giving a darn in learning Mathematics. Edited October 22, 2015 by Freelancer27 Link to comment Share on other sites More sharing options...
Bizzaro21 Posted October 22, 2015 Share Posted October 22, 2015 I suck at math, so I`ll just wish u luck and go :) Link to comment Share on other sites More sharing options...
LoseUrself2Dance Posted October 22, 2015 Author Share Posted October 22, 2015 Can't you derive Trigonometry yourself? Feels like you are asking assignment answers from the internet in the hopes someone would give you a wrong answer, without even giving a darn in learning Mathematics. Pls man, I love math. I really do. It's just that I'm stuck with this question and I have no means of finding out if I did right, so I turned to you guys. I actually did the problem, I just don't know if I did it right. So if I'm not allowed to do that then ya I'm sorry I suck at math, so I`ll just wish u luck and go :) lol thanks for the support Link to comment Share on other sites More sharing options...
08DeCiBeL80 Posted October 22, 2015 Share Posted October 22, 2015 roses are red violets are blue there is Always an asian that nows math better then you Link to comment Share on other sites More sharing options...
MegpoidBeetle Posted October 22, 2015 Share Posted October 22, 2015 Differentiation eh? Have you tried using quotient rule? Link to comment Share on other sites More sharing options...
Bizzaro21 Posted October 22, 2015 Share Posted October 22, 2015 (edited) Pls man, I love math. I really do. It's just that I'm stuck with this question and I have no means of finding out if I did right, so I turned to you guys. I actually did the problem, I just don't know if I did it right. So if I'm not allowed to do that then ya I'm sorry lol thanks for the support so I`m not the only Geek who likes it around, yay! though I just knew what Cos/sin/Tan are like 2 weeks ago.. so I`m still new to Trigonometry though I got a pun on it xD this is Trigon, Trigonometry is studying him Edited October 22, 2015 by Bizzaro21 Link to comment Share on other sites More sharing options...
TheOnlyWarBear Posted October 22, 2015 Share Posted October 22, 2015 You are dividing so you need to use Quotient rule. Look up that in yours notes (assuming you have some) or online. Then you have to kind of work backwards of the usual order of steps. Link to comment Share on other sites More sharing options...
HoakinBlackforge Posted October 22, 2015 Share Posted October 22, 2015 THE ANSWER IS YELLOW Link to comment Share on other sites More sharing options...
LoseUrself2Dance Posted October 22, 2015 Author Share Posted October 22, 2015 (edited) Differentiation eh? Have you tried using quotient rule? You are dividing so you need to use Quotient rule. Look up that in yours notes (assuming you have some) or online. Then you have to kind of work backwards of the usual order of steps. I have used the quotient rule, but this problem goes around about and everywhere D: hm, I should try to post my working This might take a while.. Edited October 22, 2015 by LoseUrself2Dance Link to comment Share on other sites More sharing options...
Renegade343 Posted October 22, 2015 Share Posted October 22, 2015 This is easy. Give me five minutes. Link to comment Share on other sites More sharing options...
LoseUrself2Dance Posted October 22, 2015 Author Share Posted October 22, 2015 This is easy. Give me five minutes. He's here :O :D Link to comment Share on other sites More sharing options...
Sakyrr Posted October 22, 2015 Share Posted October 22, 2015 I left school, i got a job, i play games i don't wanna do your maths....... Link to comment Share on other sites More sharing options...
Renegade343 Posted October 22, 2015 Share Posted October 22, 2015 He's here :O :D Scratch that, give me twelve minutes. This thing's going to be a PITA to factorize. Link to comment Share on other sites More sharing options...
MegpoidBeetle Posted October 22, 2015 Share Posted October 22, 2015 This is easy. Give me five minutes. The Mathbro has arrived! Link to comment Share on other sites More sharing options...
redfarts Posted October 22, 2015 Share Posted October 22, 2015 Dude, you should get a tutor to help you with math. I suck at math so I don't really know how to do that lol. Link to comment Share on other sites More sharing options...
(XBOX)MK Ultra K11 Posted October 22, 2015 Share Posted October 22, 2015 (edited) SO DIFFERENTIATION OF TRIGONOMETRICAL FUNCTIONS (or something, I didn't learn this in English); this problem in particular: 4x(cos x - cos 2x) f(x) = ------------------------- sin x * cos 2x Anyone would like to lend a hand to find f'(x)? :D you have sinned. :) Edit: The answer I got waaaas: 4sin2x (cos x * cos 2x * sin x - x cos 2x *+ x cosx * sin 2x * sin x) + cos x * cos22x f'(x) = ---------------------------------------------------------------------------------------------------------------------------------- cos22x * sin2x But I have no answer sheet so I can't check the answer. you have sinned. :) Edited October 22, 2015 by (XB1)MK Ultra K11 Link to comment Share on other sites More sharing options...
Magnulast Posted October 22, 2015 Share Posted October 22, 2015 (edited) hmm let me see..., what was the identities again? here's a link http://2.bp.blogspot.com/-LC3wV1fMfrw/TeQYIN8uZGI/AAAAAAAAABM/jQxF2As2NmQ/s1600/viewer_2.png Oh yeah...your supposed to split* the equation 4sin2x (cos x * cos 2x * sin x - x cos 2x *+ x cosx * sin 2x * sin x) + cos x * cos22x f'(x) = ---------------------------------------------------------------- ---------------------------------- cos22x * sin2x cos22x * sin2x If only I had a small refresher... Edited October 22, 2015 by Magnulast Link to comment Share on other sites More sharing options...
Renegade343 Posted October 22, 2015 Share Posted October 22, 2015 (edited) Alright, I got the correct solution. Your initial solution is wrong: My answer checks out with Wolfram Alpha. Edited October 22, 2015 by Renegade343 Link to comment Share on other sites More sharing options...
LoseUrself2Dance Posted October 22, 2015 Author Share Posted October 22, 2015 (edited) My brain is warm from all the thinking... Alright, I got the correct solution. Your initial solution is wrong: My answer checks out with Wolfram Alpha. WEHEW okay, a bit sad that I was wrong but glad that I have a real answer. Thanks! And thanks everyone haha Renegade343 I am 100% certain you are a wizard Edited October 22, 2015 by LoseUrself2Dance Link to comment Share on other sites More sharing options...
Renegade343 Posted October 22, 2015 Share Posted October 22, 2015 My brain is warm from all the thinking... WEHEW okay, a bit sad that I was wrong but glad that I have a real answer. Thanks! And thanks everyone haha Renegade343 I am 100% certain you are a wizard How many points is that question worth? Link to comment Share on other sites More sharing options...
Trailgamer5 Posted October 22, 2015 Share Posted October 22, 2015 help, I'm getting massive mind fucks. Basic algebra already makes my brain hurt, this S#&$ is just... Link to comment Share on other sites More sharing options...
Renegade343 Posted October 22, 2015 Share Posted October 22, 2015 help, I'm getting massive mind fucks. Basic algebra already makes my brain hurt, this S#&$ is just... I shouldn't have skipped steps when presenting. Link to comment Share on other sites More sharing options...
LoseUrself2Dance Posted October 22, 2015 Author Share Posted October 22, 2015 How many points is that question worth? No points, it was just practice question #38 out of #40. Kinda increasing in difficulty though, just not consistent Link to comment Share on other sites More sharing options...
Trailgamer5 Posted October 22, 2015 Share Posted October 22, 2015 I shouldn't have skipped steps when presenting. should I prepare for text walls? Link to comment Share on other sites More sharing options...
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