can someone please explain this shit

rC | Mythic Inconceivable!
 
more |
XBL:
PSN:
Steam:
ID: RC5908
IP: Logged

10,787 posts
ayy lmao
http://www.wolframalpha.com/input/?i=is+integral+of+sintcost+%3D%3D+-.5cos%5E2t
http://www.wolframalpha.com/input/?i=is+integral+of+sintcost+%3D%3D+.5sin%5E2t

how the fuck is sin^2(x)/2 NOT the integral of sinxcosx?

here's how i got sin^2(x)/2

integral(sinxcosxdx)
u=sinx
du=cosxdx
integral(udu) = (u^2)/2
sin^2(x)/2 + c


THIS IS FUCKING CORRECT WHY IS IT NOT
Last Edit: November 17, 2015, 02:17:23 PM by rc


 
cxfhvxgkcf-56:7
| Marty Inconceivable!
 
more |
XBL:
PSN:
Steam:
ID: SoporificSlash
IP: Logged

15,656 posts
 
This user has been blacklisted from posting on the forums. Until the blacklist is lifted, all posts made by this user have been hidden and require a Sep7agon® SecondClass Premium Membership to view.


Oh | Elite Four Invincible!
 
more |
XBL:
PSN:
Steam:
ID: Simseo
IP: Logged

3,641 posts
 
i'll do this in like 30 mins.


rC | Mythic Inconceivable!
 
more |
XBL:
PSN:
Steam:
ID: RC5908
IP: Logged

10,787 posts
ayy lmao
Lol you're retarded
no seriously i have a calc 2 exam in two hours, and this is calc 1 shit, pls help


Dopameme | Mythic Inconceivable!
 
more |
XBL: I JackItTo HALO
PSN:
Steam:
ID: Officer Nasty
IP: Logged

7,806 posts
Your love gets me so high
loooooooool nerd


Blonic the Fluxmeister | Heroic Unstoppable!
 
more |
XBL:
PSN:
Steam:
ID: Synergenic Flux
IP: Logged

1,922 posts
Dank memes coming through.
>tfw I never had to take another math class in college since freshman year 
feelsgood.jpg


Coomer | Mythic Inconceivable!
 
more |
XBL:
PSN:
Steam:
ID: Ingloriouswho98
IP: Logged

14,553 posts
 
Like (sin^2x)/2?

Because sin^2x/2 is just sin^x
Last Edit: November 17, 2015, 02:42:26 PM by Ingloriouswho98


Oh | Elite Four Invincible!
 
more |
XBL:
PSN:
Steam:
ID: Simseo
IP: Logged

3,641 posts
 
you can get -0.5*cos^2 and 0.5*sin^2

don't sweat it, you're right.


Turkey | Mythic Inconceivable!
 
more |
XBL: Viva Redemption
PSN: HurtfulTurkey
Steam: HurtfulTurkey
ID: HurtfulTurkey
IP: Logged

8,077 posts
 
how the fuck is sin^2(x)/2 NOT the integral of sinxcosx?

There are two correct answers.

"Not always" doesn't mean "isn't". Wolfram just didn't display both answers in the same question.


rC | Mythic Inconceivable!
 
more |
XBL:
PSN:
Steam:
ID: RC5908
IP: Logged

10,787 posts
ayy lmao
you can get -0.5*cos^2 and 0.5*sin^2

don't sweat it, you're right.
wolfram alpha says otherwise. also, if you evaluate it from 0 to 2pi (this is just part of a longer problem), you get 0, but it should be 3... it is 3 if you go the cosine route, but yeah.


rC | Mythic Inconceivable!
 
more |
XBL:
PSN:
Steam:
ID: RC5908
IP: Logged

10,787 posts
ayy lmao
how the fuck is sin^2(x)/2 NOT the integral of sinxcosx?

There are two correct answers.

"Not always" doesn't mean "isn't".
also, if you evaluate it from 0 to 2pi (this is just part of a longer problem), you get 0, but it should be 3... it is 3 if you go the cosine route, but yeah.


rC | Mythic Inconceivable!
 
more |
XBL:
PSN:
Steam:
ID: RC5908
IP: Logged

10,787 posts
ayy lmao


Turkey | Mythic Inconceivable!
 
more |
XBL: Viva Redemption
PSN: HurtfulTurkey
Steam: HurtfulTurkey
ID: HurtfulTurkey
IP: Logged

8,077 posts
 
how the fuck is sin^2(x)/2 NOT the integral of sinxcosx?

There are two correct answers.

"Not always" doesn't mean "isn't".
also, if you evaluate it from 0 to 2pi (this is just part of a longer problem), you get 0, but it should be 3... it is 3 if you go the cosine route, but yeah.


Well your u/du substitution is correct so just use that. Wolfram sucks ass at trig calc. It's different based on which factor you use for u.

.5sin^2(x) + C = -.5cos^2(x) + c, but their constants are not equal.
Last Edit: November 17, 2015, 02:52:34 PM by RadioactiveTurkey


Coomer | Mythic Inconceivable!
 
more |
XBL:
PSN:
Steam:
ID: Ingloriouswho98
IP: Logged

14,553 posts
 
Because sin^2x/2 is just sin^x
what

Nevermind

I was thinking of something else



Oh | Elite Four Invincible!
 
more |
XBL:
PSN:
Steam:
ID: Simseo
IP: Logged

3,641 posts
 
you get the same thing with integration by parts, you'll be fine.


R o c k e t | Mythic Smash Master
 
more |
XBL: Rocketman287
PSN:
Steam: Rocketman287
ID: Rocketman287
IP: Logged

22,970 posts
I neither fear, nor despise.
I remember having to do this shit


ΚΑΤΑΝΑΛΩΤΗΣ | Mythic Invincible!
 
more |
XBL:
PSN:
Steam:
ID: TrussingDoor
IP: Logged

7,667 posts
"A time is coming when men will go mad, and when they see someone who is not mad, they will attack him saying, 'You are mad, you are not like us'."
-Saint Anthony the Great
This user has been blacklisted from posting on the forums. Until the blacklist is lifted, all posts made by this user have been hidden and require a Sep7agon® SecondClass Premium Membership to view.


Dan | Heroic Unstoppable!
 
more |
XBL:
PSN:
Steam:
ID: Daniel Fortesque
IP: Logged

2,359 posts
 
Math sucks.


 
DAS B00T x2
| Cultural Appropriator
 
more |
XBL:
PSN:
Steam:
ID: DAS B00T x2
IP: Logged

37,630 posts
This is not the greatest sig in the world, no. This is just a tribute.
I learned this in high school and never used it again in five years. Now this thread is literally a foreign language to me.


Desty | Mythic Inconceivable!
 
more |
XBL:
PSN:
Steam:
ID: DTEDesty
IP: Logged

10,577 posts
 
Holy shit what the fuck are you guys doing?

Rc asked for help, he gets help, but then these motherfuckers show up and start talking about how they used to do the same thing, and how the world has changed for them.

What is with you people?

What I'm trying to say in my autistic ramblings is that your platitudes aren't doing anything for the thread, so you must be doing it for yourselves, which is fine in some threads, but this thread isn't a thread for discussion about personal experiences or whatever. This is a thread specifically about a certain math problem.

also, 'mirin peoples' math skills.
Last Edit: November 17, 2015, 03:48:35 PM by The Meta Madman Destyyy👌


Oh | Elite Four Invincible!
 
more |
XBL:
PSN:
Steam:
ID: Simseo
IP: Logged

3,641 posts
 
Holy shit what the fuck are you guys doing?

Rc asked for help, he gets help, but then these motherfuckers show up and start talking about how they used to do the same thing, and how the world has changed for them.

What is with you people?
le funposting


rC | Mythic Inconceivable!
 
more |
XBL:
PSN:
Steam:
ID: RC5908
IP: Logged

10,787 posts
ayy lmao
how the fuck is sin^2(x)/2 NOT the integral of sinxcosx?

There are two correct answers.

"Not always" doesn't mean "isn't".
also, if you evaluate it from 0 to 2pi (this is just part of a longer problem), you get 0, but it should be 3... it is 3 if you go the cosine route, but yeah.


Well your u/du substitution is correct so just use that. Wolfram sucks ass at trig calc. It's different based on which factor you use for u.

.5sin^2(x) + C = -.5cos^2(x) + c, but their constants are not equal.
Why do I get two different answers when I evaluate it though? I just wanna understand what went wrong.

Because my understanding is that the constant doesn't matter when you're solving a definite integral.
Last Edit: November 17, 2015, 04:00:27 PM by rc


R o c k e t | Mythic Smash Master
 
more |
XBL: Rocketman287
PSN:
Steam: Rocketman287
ID: Rocketman287
IP: Logged

22,970 posts
I neither fear, nor despise.
Holy shit what the fuck are you guys doing?

Rc asked for help, he gets help, but then these motherfuckers show up and start talking about how they used to do the same thing, and how the world has changed for them.

What is with you people?

What I'm trying to say in my autistic ramblings is that your platitudes aren't doing anything for the thread, so you must be doing it for yourselves, which is fine in some threads, but this thread isn't a thread for discussion about personal experiences or whatever. This is a thread specifically about a certain math problem.

also, 'mirin peoples' math skills.
Read the thread, people helped him

Good God man read before you type a wall


Desty | Mythic Inconceivable!
 
more |
XBL:
PSN:
Steam:
ID: DTEDesty
IP: Logged

10,577 posts
 
Holy shit what the fuck are you guys doing?

Rc asked for help, he gets help, but then these motherfuckers show up and start talking about how they used to do the same thing, and how the world has changed for them.

What is with you people?

What I'm trying to say in my autistic ramblings is that your platitudes aren't doing anything for the thread, so you must be doing it for yourselves, which is fine in some threads, but this thread isn't a thread for discussion about personal experiences or whatever. This is a thread specifically about a certain math problem.

also, 'mirin peoples' math skills.
Read the thread, people helped him

Good God man read before you type a wall
Read the reply, I wrote that people helped him.


 
DAS B00T x2
| Cultural Appropriator
 
more |
XBL:
PSN:
Steam:
ID: DAS B00T x2
IP: Logged

37,630 posts
This is not the greatest sig in the world, no. This is just a tribute.
Desty is why I'm an anti-vaxer.


R o c k e t | Mythic Smash Master
 
more |
XBL: Rocketman287
PSN:
Steam: Rocketman287
ID: Rocketman287
IP: Logged

22,970 posts
I neither fear, nor despise.
Holy shit what the fuck are you guys doing?

Rc asked for help, he gets help, but then these motherfuckers show up and start talking about how they used to do the same thing, and how the world has changed for them.

What is with you people?

What I'm trying to say in my autistic ramblings is that your platitudes aren't doing anything for the thread, so you must be doing it for yourselves, which is fine in some threads, but this thread isn't a thread for discussion about personal experiences or whatever. This is a thread specifically about a certain math problem.

also, 'mirin peoples' math skills.
Read the thread, people helped him

Good God man read before you type a wall
Read the reply, I wrote that people helped him.

who cares if we mention we used to do calculus?

just you


Assassin 11D7 | Mythic Inconceivable!
 
more |
XBL: Assassin 11D7
PSN:
Steam:
ID: Assassin 11D7
IP: Logged

10,059 posts
"flaming nipple chops"-Your host, the man they call Ghost.

To say, 'nothing is true', is to realize that the foundations of society are fragile, and that we must be the shepherds of our own civilization. To say, 'everything is permitted', is to understand that we are the architects of our actions, and that we must live with their consequences, whether glorious or tragic.
how the fuck is sin^2(x)/2 NOT the integral of sinxcosx?

There are two correct answers.

"Not always" doesn't mean "isn't".
also, if you evaluate it from 0 to 2pi (this is just part of a longer problem), you get 0, but it should be 3... it is 3 if you go the cosine route, but yeah.


Well your u/du substitution is correct so just use that. Wolfram sucks ass at trig calc. It's different based on which factor you use for u.

.5sin^2(x) + C = -.5cos^2(x) + c, but their constants are not equal.
Why do I get two different answers when I evaluate it though? I just wanna understand what went wrong.

Because my understanding is that the constant doesn't matter when you're solving a definite integral.
Probably has to do with the integral of Sinx cancelling out, if you remember the unit circle you can go to something like pi/2 and multiply the integral by 4, because you are integrating 4 values of pi/2  = to one value of 2pi.


15321598721 | Heroic Posting Rampage
 
more |
XBL:
PSN:
Steam:
ID: Baha
IP: Logged

1,094 posts
 
http://www.wolframalpha.com/input/?i=is+integral+of+sintcost+%3D%3D+-.5cos%5E2t
http://www.wolframalpha.com/input/?i=is+integral+of+sintcost+%3D%3D+.5sin%5E2t

how the fuck is sin^2(x)/2 NOT the integral of sinxcosx?

here's how i got sin^2(x)/2

integral(sinxcosxdx)
u=sinx
du=cosxdx
integral(udu) = (u^2)/2
sin^2(x)/2 + c


THIS IS FUCKING CORRECT WHY IS IT NOT
the integral of sinxcosxdx isn't sin^2(x)/2
it's sin^2(x)/2 + C

sin^2(x) + cos^(x) = 1
sin^2(x) = 1 - cos^2(x)
sin^2(x)/2 = .5 - cos^2(x)/2

sin^2(x)/2 + C is equivalent to  -cos^2(x)/2 + C
Last Edit: November 17, 2015, 09:53:19 PM by Baha


CIS | Legendary Invincible!
 
more |
XBL:
PSN:
Steam:
ID: AutisticComputer
IP: Logged

3,310 posts
 
Desty is why I'm an anti-vaxer.

Destyposting is love, Destyposting is life.


rC | Mythic Inconceivable!
 
more |
XBL:
PSN:
Steam:
ID: RC5908
IP: Logged

10,787 posts
ayy lmao
http://www.wolframalpha.com/input/?i=is+integral+of+sintcost+%3D%3D+-.5cos%5E2t
http://www.wolframalpha.com/input/?i=is+integral+of+sintcost+%3D%3D+.5sin%5E2t

how the fuck is sin^2(x)/2 NOT the integral of sinxcosx?

here's how i got sin^2(x)/2

integral(sinxcosxdx)
u=sinx
du=cosxdx
integral(udu) = (u^2)/2
sin^2(x)/2 + c


THIS IS FUCKING CORRECT WHY IS IT NOT
the integral of sinxcosxdx isn't sin^2(x)/2
it's sin^2(x)/2 + C

sin^2(x) + cos^(x) = 1
sin^2(x) = 1 - cos^2(x)
sin^2(x)/2 = .5 - cos^2(x)/2

sin^2(x)/2 + C is equivalent to  -cos^2(x)/2 + C
but the constant doesn't matter in a definite integral, right?