Board 8 > Board 8 math people, got a question for you (calc 2)

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Anagram 10/16/17 8:37:46 PM #1:	I've got a problem. I've tried to use every method I know to solve the integral and I've tried an online integral solver. It told me that it couldn't help. Here's the problem: If anyone knows a strategy I can try, I'd be happy to hear it. All I know is that u-subs and trig subs are useless, and those are my main methods. --- Not changing this sig until I decide to change this sig. Started: July 6, 2005 <cite>Anagram posted [p:888566240] in Board 8 ma... [t:75886889]...</cite> <quote>I've got a problem. I've tried to use every method I know to solve the integral and I've tried an online integral solver. It told me that it couldn't help. Here's the problem: If anyone knows a strategy I can try, I'd be happy to hear it. All I know is that u-subs and trig subs are useless, and those are my main methods.</quote> ... Copied to Clipboard!
Logicblade 10/16/17 8:45:04 PM #2:	So substituting u=x^2 and du = 2x dx doesn't work? --- Spare me your obsolete empathy The voice of sympathy means nothing to me <cite>Logicblade posted [p:888566685] in Board 8 ma... [t:75886889]...</cite> <quote>So substituting u=x^2 and du = 2x dx doesn't work?</quote> ... Copied to Clipboard!
Anagram 10/16/17 9:08:51 PM #3:	Logicblade posted... So substituting u=x^2 and du = 2x dx doesn't work? Just checked. I don't think it will? --- Not changing this sig until I decide to change this sig. Started: July 6, 2005 <cite>Anagram posted [p:888568149] in Board 8 ma... [t:75886889]...</cite> <quote><cite>Logicblade posted...</cite> <quote>So substituting u=x^2 and du = 2x dx doesn't work?</quote> Just checked. I don't think it will?</quote> ... Copied to Clipboard!
SeabassDebeste 10/16/17 9:11:43 PM #4:	are you sure you haven't made a typo? can you take a picture of the question as is? --- yet all sailors of all sorts are more or less capricious and unreliable - they live in the varying outer weather, and they inhale its fickleness <cite>SeabassDebeste posted [p:888568303] in Board 8 ma... [t:75886889]...</cite> <quote>are you sure you haven't made a typo? can you take a picture of the question as is?</quote> ... Copied to Clipboard!
tyder21 10/16/17 9:12:37 PM #5:	Yeah, there's no way that's the question. That would be incredibly difficult to solve. --- http://letterboxd.com/tyder21/ BKSheikah Was Here <cite>tyder21 posted [p:888568360] in Board 8 ma... [t:75886889]...</cite> <quote>Yeah, there's no way that's the question. That would be incredibly difficult to solve.</quote> ... Copied to Clipboard!
greengravy294 10/16/17 9:16:24 PM #6:	Did you try wolfram alpha --- http://i.imgur.com/jknf665.png <cite>greengravy294 posted [p:888568588] in Board 8 ma... [t:75886889]...</cite> <quote>Did you try wolfram alpha</quote> ... Copied to Clipboard!
azuarc 10/16/17 9:16:26 PM #7:	Unless I'm misreading this, it just wants you to simplify, and not to do any actual calculus. So multiply the two radicands. Sqrt(-4x^4+15x^2+4) --- http://imgur.com/ekqlssN <cite>azuarc posted [p:888568589] in Board 8 ma... [t:75886889]...</cite> <quote>Unless I'm misreading this, it just wants you to simplify, and not to do any actual calculus. So multiply the two radicands. Sqrt(-4x^4+15x^2+4)</quote> ... Copied to Clipboard!
tyder21 10/16/17 9:18:20 PM #8:	azuarc posted... Unless I'm misreading this, it just wants you to simplify, and not to do any actual calculus. So multiply the two radicands. Sqrt(-4x^4+15x^2+4) I think what he posted was a screencap of the integral solver he tried to use. Not the original question. --- http://letterboxd.com/tyder21/ BKSheikah Was Here <cite>tyder21 posted [p:888568707] in Board 8 ma... [t:75886889]...</cite> <quote><cite>azuarc posted...</cite> <quote>Unless I'm misreading this, it just wants you to simplify, and not to do any actual calculus. So multiply the two radicands. Sqrt(-4x^4+15x^2+4)</quote> I think what he posted was a screencap of the integral solver he tried to use. Not the original question.</quote> ... Copied to Clipboard!
azuarc 10/16/17 9:22:25 PM #9:	And the goal is to integrate that entire expression? The fact that the machines can't do it should tell you all you need to know. --- http://imgur.com/ekqlssN <cite>azuarc posted [p:888568961] in Board 8 ma... [t:75886889]...</cite> <quote>And the goal is to integrate that entire expression? The fact that the machines can't do it should tell you all you need to know.</quote> ... Copied to Clipboard!
Anagram 10/16/17 9:23:10 PM #10:	The original question is 7a in this sheet: I know you obtain the answer by Integral from a to b of 2pif(x)(rad(1+(dy/dx)^2)dx. dy/dx is just the derivative of the original function, which is -2x, which becomes rad(1+4x^2). --- Not changing this sig until I decide to change this sig. Started: July 6, 2005 <cite>Anagram posted [p:888569016] in Board 8 ma... [t:75886889]...</cite> <quote>The original question is 7a in this sheet: I know you obtain the answer by Integral from a to b of 2pif(x)(rad(1+(dy/dx)^2)dx. dy/dx is just the derivative of the original function, which is -2x, which becomes rad(1+4x^2).</quote> ... Copied to Clipboard!
azuarc 10/16/17 9:25:07 PM #11:	So we need the surface area of a truncated sphere. --- http://imgur.com/ekqlssN <cite>azuarc posted [p:888569140] in Board 8 ma... [t:75886889]...</cite> <quote>So we need the surface area of a truncated sphere.</quote> ... Copied to Clipboard!
azuarc 10/16/17 9:28:20 PM #12:	What you need to recall about surface area of a rotated figure is that you're basically adding up circumferences over and over. So if sqrt(4-x^2) is the radius, the circumference is 2pisqrt(4-x^2). You want to be integrating the "slices" of that from -1 to 1. --- http://imgur.com/ekqlssN <cite>azuarc posted [p:888569349] in Board 8 ma... [t:75886889]...</cite> <quote>What you need to recall about surface area of a rotated figure is that you're basically adding up circumferences over and over. So if sqrt(4-x^2) is the radius, the circumference is 2pisqrt(4-x^2). You want to be integrating the "slices" of that from -1 to 1.</quote> ... Copied to Clipboard!
Janus5k 10/16/17 9:29:02 PM #13:	Anagram posted... dy/dx is just the derivative of the original function, which is -2x Found your problem. You forgot the square root. --- "Those who cast the vote decide nothing. Those who count the vote decide everything." <cite>Janus5k posted [p:888569391] in Board 8 ma... [t:75886889]...</cite> <quote><cite>Anagram posted...</cite> <quote>dy/dx is just the derivative of the original function, which is -2x</quote> Found your problem. You forgot the square root.</quote> ... Copied to Clipboard!
NFUN 10/16/17 9:29:42 PM #14:	anagram. are you sure your equation is right? sure you're sure? --- Thus is our treaty written, thus is our agreement made. Thought is the arrow of time; memory never fades. What was asked is given; the price is paid. ARF <cite>NFUN posted [p:888569425] in Board 8 ma... [t:75886889]...</cite> <quote>anagram. are you sure your equation is right? sure you're sure?</quote> ... Copied to Clipboard!
azuarc 10/16/17 9:29:51 PM #15:	Anagram posted... I know you obtain the answer by...(rad(1+(dy/dx)^2)dx. No need for the arclength formula. --- http://imgur.com/ekqlssN <cite>azuarc posted [p:888569430] in Board 8 ma... [t:75886889]...</cite> <quote><cite>Anagram posted...</cite> <quote>I know you obtain the answer by...(rad(1+(dy/dx)^2)dx.</quote> No need for the arclength formula.</quote> ... Copied to Clipboard!
Anagram 10/16/17 9:30:49 PM #16:	Janus5k posted... Anagram posted... dy/dx is just the derivative of the original function, which is -2x Found your problem. You forgot the square root. Welp Time to commit math seppuku --- Not changing this sig until I decide to change this sig. Started: July 6, 2005 <cite>Anagram posted [p:888569495] in Board 8 ma... [t:75886889]...</cite> <quote><cite>Janus5k posted...</cite> <quote><cite>Anagram posted...</cite> <quote>dy/dx is just the derivative of the original function, which is -2x</quote> Found your problem. You forgot the square root.</quote> Welp Time to commit math seppuku</quote> ... Copied to Clipboard!
NFUN 10/16/17 9:31:44 PM #17:	I finally happened. We got Anagram'd in an Anagram math topic. --- Thus is our treaty written, thus is our agreement made. Thought is the arrow of time; memory never fades. What was asked is given; the price is paid. ARF <cite>NFUN posted [p:888569549] in Board 8 ma... [t:75886889]...</cite> <quote>I finally happened. We got Anagram'd in an Anagram math topic.</quote> ... Copied to Clipboard!
Anagram 10/16/17 9:31:59 PM #18:	azuarc posted... Anagram posted... I know you obtain the answer by...(rad(1+(dy/dx)^2)dx. No need for the arclength formula. And why wouldn't I need the arclength formula? In all of my notes it's used for this kind of problem. --- Not changing this sig until I decide to change this sig. Started: July 6, 2005 <cite>Anagram posted [p:888569560] in Board 8 ma... [t:75886889]...</cite> <quote><cite>azuarc posted...</cite> <quote><cite>Anagram posted...</cite> <quote>I know you obtain the answer by...(rad(1+(dy/dx)^2)dx.</quote> No need for the arclength formula.</quote> And why wouldn't I need the arclength formula? In all of my notes it's used for this kind of problem.</quote> ... Copied to Clipboard!
tyder21 10/16/17 9:36:52 PM #19:	Pretty sure the answer is 8pi if you want to check against me. --- http://letterboxd.com/tyder21/ BKSheikah Was Here <cite>tyder21 posted [p:888569897] in Board 8 ma... [t:75886889]...</cite> <quote>Pretty sure the answer is 8pi if you want to check against me.</quote> ... Copied to Clipboard!
Anagram 10/16/17 9:38:40 PM #20:	tyder21 posted... Pretty sure the answer is 8pi if you want to check against me. I'm still solving the problem, but that is correct (I have the answer sheet). --- Not changing this sig until I decide to change this sig. Started: July 6, 2005 <cite>Anagram posted [p:888569992] in Board 8 ma... [t:75886889]...</cite> <quote><cite>tyder21 posted...</cite> <quote>Pretty sure the answer is 8pi if you want to check against me.</quote> I'm still solving the problem, but that is correct (I have the answer sheet).</quote> ... Copied to Clipboard!
SeabassDebeste 10/16/17 9:40:36 PM #21:	i'm shocked that this happened --- yet all sailors of all sorts are more or less capricious and unreliable - they live in the varying outer weather, and they inhale its fickleness <cite>SeabassDebeste posted [p:888570116] in Board 8 ma... [t:75886889]...</cite> <quote>i'm shocked that this happened</quote> ... Copied to Clipboard!
Anagram 10/16/17 10:23:19 PM #22:	tyder21 posted... Pretty sure the answer is 8pi if you want to check against me. By the way, did you solve this with arclength formula? --- Not changing this sig until I decide to change this sig. Started: July 6, 2005 <cite>Anagram posted [p:888572809] in Board 8 ma... [t:75886889]...</cite> <quote><cite>tyder21 posted...</cite> <quote>Pretty sure the answer is 8pi if you want to check against me.</quote> By the way, did you solve this with arclength formula?</quote> ... Copied to Clipboard!
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Board 8 > Board 8 math people, got a question for you (calc 2) (+) Yeah! (+)

Board 8 > Board 8 math people, got a question for you (calc 2)