Arkhi Posted March 1, 2016 Share Posted March 1, 2016 Welcome, nerds. Let's do math/s. If you're looking for help with some math problem(s) or... something pertaining to mathematics, post it here. You don't need to list what level of mathematics it is, though labeling a problem as such can help narrow down who is capable of helping best. Necroposting shouldn't be an issue, so feel free to post here whenever. Avoid double-posting- an exception is made if there's been 24 hours between a post you made and another one you'd like to make. Preferably, the questions will be serious, but do whatever you please. 1 2 3 go! Quote Link to comment Share on other sites More sharing options...
Shadow Roxas Posted March 1, 2016 Share Posted March 1, 2016 Hey Arkhi I'm having a major problem with some mathematics. I've been wracking my brain over and over and it even has scientists baffled.It's a problem that's been plaguing my life since I was first introduced to the mere concept of math.Arkhi... buddy, friend pal chum...What is the answer when you take two and add another two? Quote Link to comment Share on other sites More sharing options...
Tacos Posted March 1, 2016 Share Posted March 1, 2016 Can you help me with this one? It baffles me constantly and I'm sure only a master mathematician like yourself can figure it out. QTπ=U Quote Link to comment Share on other sites More sharing options...
Arkhi Posted March 1, 2016 Author Share Posted March 1, 2016 What is the answer when you take two and add another two? hey there buddy chum pal friend buddy pal chum bud friend fella bruther amigo pal buddy friend chummy chum chum pal According to the techniques employed by Bobobo, there is a 90% probability of the answer being 7, a 10% chance of the answer being 6, and a 100% chance of the answer being 4. Can you help me with this one? It baffles me constantly and I'm sure only a master mathematician like yourself can figure it out. QTπ=U I'm afraid those two terms aren't equivalent less than fraction bar three Quote Link to comment Share on other sites More sharing options...
Rosesong Posted March 1, 2016 Share Posted March 1, 2016 Hey Arkhi I'm having a major problem with some mathematics. I've been wracking my brain over and over and it even has scientists baffled. It's a problem that's been plaguing my life since I was first introduced to the mere concept of math. Arkhi... buddy, friend pal chum... What is the answer when you take two and add another two? hey there buddy chum pal friend buddy pal chum bud friend fella bruther amigo pal buddy friend chummy chum chum pal According to the techniques employed by Bobobo, there is a 90% probability of the answer being 7, a 10% chance of the answer being 6, and a 100% chance of the answer being 4. Wait Professor Arki sir, I though there was a good possibility of the answer being fish. Could you please grant me your insight and wisdom to understand how fish is not a viable answer for Roxie's challenging query? Quote Link to comment Share on other sites More sharing options...
Arkhi Posted March 1, 2016 Author Share Posted March 1, 2016 Wait Professor Arki sir, I though there was a good possibility of the answer being fish. Could you please grant me your insight and wisdom to understand how fish is not a viable answer for Roxie's challenging query? i is an imaginary number and fish has an i in it. Imaginary numbers don't exist. Thus, fish is not a real answer. Quote Link to comment Share on other sites More sharing options...
Rosesong Posted March 1, 2016 Share Posted March 1, 2016 OOOOOOOOOOOH, I understand now! That's why 7 and 7 cannot equal a triangle, right? But, can 3 and 3 equal 8? Or does it equal snowman instead? Quote Link to comment Share on other sites More sharing options...
Tacos Posted March 1, 2016 Share Posted March 1, 2016 I'm afraid those two terms aren't equivalent less than fraction bar three Ok but 1+1=Window right? Because I'm just trying to find a window into your heart. Quote Link to comment Share on other sites More sharing options...
Arkhi Posted March 1, 2016 Author Share Posted March 1, 2016 OOOOOOOOOOOH, I understand now! That's why 7 and 7 cannot equal a triangle, right? Contrary to popular belief, 7 and 7 may equal a triangle- if you have three 7s- one for each side of the triangle- you have 21, and 21 is legal. So you can have a triangle made of 7s. But, can 3 and 3 equal 8? Ok but 1+1=Window right? Because I'm just trying to find a window into your heart. Less than three Also, this is one of the search results for "Love calculator", imagine I had Photoshop, experience, and fixed this to say "Tacos" and "Arkhi" Quote Link to comment Share on other sites More sharing options...
Chevaleresse Posted March 1, 2016 Share Posted March 1, 2016 (edited) trying to integrate −2ln(2x+1)dx and after doing IBP i get -x^2ln(2x+1) - int(-x^2/2x+1) which makes me sad Edited March 1, 2016 by Arkhi Worked it out on the server Quote Link to comment Share on other sites More sharing options...
Hiss13 Posted March 1, 2016 Share Posted March 1, 2016 trying to integrate −2ln(2x+1)dx and after doing IBP i get -x^2ln(2x+1) - int(-x^2/2x+1) which makes me sad Based on that you're using the wrong u and dv. u=ln(2x+1), dv=dx, carry the -2 out of the integral. Quote Link to comment Share on other sites More sharing options...
Arkhi Posted March 1, 2016 Author Share Posted March 1, 2016 Murdoc mentioned trying that, but then worked it out with Wolfram Alpha. Quote Link to comment Share on other sites More sharing options...
Hiss13 Posted March 1, 2016 Share Posted March 1, 2016 Murdoc mentioned trying that, but then Wolfram Alpha'd it.Oh. But even so, just doing it in my head, that method should work out. Don't know why it wouldn't... Quote Link to comment Share on other sites More sharing options...
Arkhi Posted March 1, 2016 Author Share Posted March 1, 2016 It works out to xln(2x+1) - int(2x/(2x+1)dx From there, I managed to get xln(2x+1) - [2x3 + x2 + int(2x2 dx)] And from there, xln(2x+1) - 2x3 - x2 - (2/3)x3 + C Quote Link to comment Share on other sites More sharing options...
Hiss13 Posted March 1, 2016 Share Posted March 1, 2016 No. You're definitely missing an ln there. This step is right xln(2x+1) - int(2xdx/(2x+1)) Next step is to u-sub with 2x+1=u, u-1=2x, dx=du/2 xln(2x+1)-.5*int((u-1)du/u)=xln(2x+1)-.5*int(du)-.5*int(-du/u) Which goes to xln(2x+1)-.5*u+.5*ln(u)=xln(2x+1)-.5*(2x+1)+.5*ln(2x+1) Which then goes to (x+.5)(ln(2x+1)-1) Multiply out the -2 we took out the integral and add the C -(2x+1)(ln(2x+1)-1)+C Quote Link to comment Share on other sites More sharing options...
Jelly Posted March 1, 2016 Share Posted March 1, 2016 haha nerds typing out ur math problems instead of crying over them Quote Link to comment Share on other sites More sharing options...
Cool Girl Posted March 2, 2016 Share Posted March 2, 2016 (edited) Hey guys, so I need help with some pre-calculus problems. Bear with me, it's a lot of problems, but I really need help, so without further ado, here they are: On problem 45, you have to find all solutions of the equation in the interval [0, 2π). This is the problem cos 4x (cos x-1) = 0 On problem 47, you have to use inverse functions where needed to find all solutions of the equation in the interval [0, 2π). sin2x - 2 sin x = 0 On problem 51 and 53, you have to find the exact value of the sine, cosine, and tangent of the angle by using a sum or difference formula. 51) 285°= 315°-30° 53) 25π/12 = 11π/6 + π/4 On problem 69, you have to use double-angle formulas to verify the identity algebraically and use a graphing utility to confirm it graphically. sin 4x = 8 cos3x sin x - 4 cos x sin x On problem 79 and 81, you have to use the half-angle formulas to determine the exact values of the sine, cosine, and tangent of the angle. 79) - 75° 81) 19π/12 On problem 83, you have to use half-angle formulas to simplify the expression - √1 + cos 10x /2 That is all the problems I needed help on. Thanks for taking the time to read these and I hope you could help out in some way! Edited March 2, 2016 by Cool Girl Quote Link to comment Share on other sites More sharing options...
Hiss13 Posted March 2, 2016 Share Posted March 2, 2016 45) (cos4x)(cosx -1)=0 Therefore cos4x=0 or cosx=1 If the former, 4x=π/2 or 4x=3π/2 x=π/8 or 3π/8. Therefore, {x=kπ/8 |k=2n+1|n is an integer in [0,3]} or, x=0, 2π (for when cosx=1). 47) sin2x -2*sinx=0 sinx(sinx-2)=0 sinx=0 when x=0 or 2π sinx cannot equal 2 'Nuff said. 51 and 53 are self-explanatory. You have all the sums and differences there so the best thing to do is use the formulae. Plug and chug. All of those are variants of 45 and 30 degrees. 69) sin4x=8cos3xsinx-4cosxsinx =4cosxsinx(2cos3x-1) The first part equals 2sin2x, the second equals cos2x =2sin2xcos2x=sin4x 79) I'll just give you the hint that 75=150/2 81) 19π/12=(19π/6)/2 83) That is literally the half angle formula for cosx except x is replaced with 10x, so it's equal to cos5x. Happy math-ing~ Quote Link to comment Share on other sites More sharing options...
Cool Girl Posted March 2, 2016 Share Posted March 2, 2016 (edited) Wow, you make high school pre-calculus so easy. Thanks! Edited March 2, 2016 by Cool Girl Quote Link to comment Share on other sites More sharing options...
Spineblade Posted March 2, 2016 Share Posted March 2, 2016 Are people taking this thread seriously? I hope people are taking this thread seriously... I think the answer to B, part (i) is 3a^2 = 6ax + c , but I'm not 100% sure. As for part (ii), I have no idea what I'm doing. Since it's only worth 1 mark, it must be fairly simple, but I must just be missing the point. Any help? Quote Link to comment Share on other sites More sharing options...
Hiss13 Posted March 2, 2016 Share Posted March 2, 2016 (edited) Hiss answers math problems. I has hijacked this thread. For b(i) y'=6x so, using Point-slope form: (y-3a2)=6a(x-a) y-3a2=6ax-6a2 Tangent: y=6ax+3a2 For b(ii) Plug (0,-12) into that tangent line equation Edited March 2, 2016 by Hiss13 Quote Link to comment Share on other sites More sharing options...
Dhanush D Bhatt Posted March 2, 2016 Share Posted March 2, 2016 (edited) Oooooh Maths thread, why didn't i see this earlier??Ok Spine, here goesYou have y - 3x^2Slope of a tangent = dy = 6x dxTherefore, slope at the given point = 6(a) = 6aEquation of a line can be written as y = mx + cWe know that m = slope = 6aSo y = 6ax + cIn order to find the value of c, we use the fact that the point (a,3a^2) lies on the line. So substituting the point into the line equation,3a^2 = 6a^2 + c which gives us c = -3a^2So the required equation isy = 3ax - 3a^2As for the second part, we just substitute the point (0,-12) into the above line equation.So, -12 = 3a(0) -3a^2So we get a^2 = 4 So a = 2 or -2And that's about it. I hope the solution is clear enough.Edit : Hiss is super ninja Edited March 2, 2016 by Dhanush D Bhatt Quote Link to comment Share on other sites More sharing options...
Spineblade Posted March 2, 2016 Share Posted March 2, 2016 Ah, right, I hadn't realised the equation for the tangent still had to have y as the subject despite being in terms of a. Silly me. Thanks, you two! Quote Link to comment Share on other sites More sharing options...
Ironbound Posted March 4, 2016 Share Posted March 4, 2016 This is such a nice thread. Too bad I don't deal with higher math anymore....perhaps I can start an accounts/tax thread, but there likely won't be many to participate in it... ...rats. Quote Link to comment Share on other sites More sharing options...
Alaris Posted March 7, 2016 Share Posted March 7, 2016 (edited) Can statistics also be discussed? : P Edited March 7, 2016 by Alaris Quote Link to comment Share on other sites More sharing options...
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