#1

Im just going through some Maths exam papers, and I've come across a problem that I can't, for the life of me, remember how to do, and I cannot find any of my notes on it.

The graph of y = sin x is plotted between the limits of 0 and pi/2. Basically, the line is rotated 360degrees at a right angle to the x-axis, so it wraps around, and forms a cone, of sorts.

How do you find the volume of the shape?

I apologize if it isn't particularly clear what I'm asking, I can go get the paper, and copy the question out word for word.

The graph of y = sin x is plotted between the limits of 0 and pi/2. Basically, the line is rotated 360degrees at a right angle to the x-axis, so it wraps around, and forms a cone, of sorts.

How do you find the volume of the shape?

I apologize if it isn't particularly clear what I'm asking, I can go get the paper, and copy the question out word for word.

#2

This is why you don't do maths.

#3

wat

If it was rotated 360 degrees it wouldn't do sh

If it was rotated 360 degrees it wouldn't do sh

*it.*
#4

the size of the area underneath pi * sin^2 is your answer

i presume you know how to do that

i presume you know how to do that

#5

A line rotated at a 360 degree angle?

Wtf is this ****?

Wtf is this ****?

#6

wat

If it was rotated 360 degrees it wouldn't do shit.

wrapped around a cone. i'd imagine.

#7

Check your formula book, theres a formula with something to do with the integral of the equation and pi

#8

Integrate sin²x from 0 to pi/2 and multiply that by pi.

#9

Integrate sin²x from 0 to pi/2 and multiply that by pi.

Then divide by 0.

#10

you need to form an equation for tha radius of the conical figure that relates to the position on the x-axis....... inegrate this between your limtis and BANG!!!! donksi's........ unless ur problems are different to mine that is...........

#11

Then divide by 0.

no the person who you quoted was actually right

#12

Could you please copy the question out...

cause if you integrate the curve then u'd get the surface area of the cone and not the volume enclosed by the cone..

ya so copy the question out cause this seems interesting....i'm waitin

cause if you integrate the curve then u'd get the surface area of the cone and not the volume enclosed by the cone..

ya so copy the question out cause this seems interesting....i'm waitin

#13

Could you please copy the question out...

cause if you integrate the curve then u'd get the surface area of the cone and not the volume enclosed by the cone..

ya so copy the question out cause this seems interesting....i'm waitin

the integral of a curve is te area under it so if you rotate it you will get volume

#14

no the person who you quoted was actually right

...

#15

the integral of a curve is te area under it so if you rotate it you will get volume

Ahem ok...

Cut out a n shaped piece of paper...which will be a representation of the curve...

Now if you integrate the area under the curve you get the area of the piece of paper you have...

If you make a cone out of that piece of paper the area of the paper used will not give you the volume of the cone...it'll be the surface area of the cone

See ??

#16

Ahem ok...

Cut out a n shaped piece of paper...which will be a representation of the curve...

Now if you integrate the area under the curve you get the area of the piece of paper you have...

If you make a cone out of that piece of paper the area of the paper used will not give you the volume of the cone...it'll be the surface area of the cone

See ??

No, that's not the cone you're looking for. This is a solids of revolution type of question.

You spin the sin curve around the x-axis, making a 3d shape out of that. This is the volume we're looking for.

#17

http://www.maths.abdn.ac.uk/~igc/tch/ma1002/int/node22.html

That page explains it.

Bassically you square the function, multiply by Pi, and intergrate between the limit! Thats all there is to it

That page explains it.

Bassically you square the function, multiply by Pi, and intergrate between the limit! Thats all there is to it

#18

Oh k k....my bad....i thought you were making a cone using the curve.

Yeah i get it...sorry

Yeah i get it...sorry

#19

...I finished the question about an hour and a half ago...

#20

...I finished the question about an hour and a half ago...

Oh well. Some of the replies we're quite funny (in a really geeky way :/)

#21

#22

no the person who you quoted was actually right

Lol, you don't understand maths do you?

#23

integrate?

#24

Im just going through some Maths exam papers, and I've come across a problem that I can't, for the life of me, remember how to do, and I cannot find any of my notes on it.

The graph of y = sin x is plotted between the limits of 0 and pi/2. Basically, the line is rotated 360degrees at a right angle to the x-axis, so it wraps around, and forms a cone, of sorts.

How do you find the volume of the shape?

I apologize if it isn't particularly clear what I'm asking, I can go get the paper, and copy the question out word for word.

you need to integrate (sinx)² between 0 an pi/2, and then multiply it all by pi:

π∫(sinx)²dx

between 0 and π/2, where 0 is the lower limit and π/2 is the upper limit (it would be drawn on the integral sign but i dont know how to do it on the computer).

basically, you integrate (sinx)². then substitute π/2 for x. do the same thing again but this time substitute 0 for x. subtract the second value from the first and you have the volume of the shape.

good luck.