integration question of NOV 2010

[kamina1]

wat was the answer man..???...and how do we integrate a line to find volume..??

 

[PlanetMaster]

In order to find the area under a graph we need to state the lower and upper values of x. These values are called the limits and are written at the top and bottom of the integral sign to indicate which area is being found.

Example:

To find this area we have to integrate between x = 1 and x = 4. This is written as:

To evaluate this we integrate and then substitute in the limits, subtracting the value of the lower limit from the value of the higher limit.

 

[umer]

wat was the answer man..???...and how do we integrate a line to find volume..??

i gt 0.91pie as my final ans.first i found out the volume under curve tht was 2pie with having limits 5 and 0. Then Volume under the line with havin limits 5 and 0 an the ans was 2.91pie...sbtracted volume of curve from volume of line so the ans was 0.91pie..

 

[soumayya]

The exact answer was 11/12 pie...

 

[kamina1]

hey tell me one thing...my volume under curve was correct...i.e.2pi...i integrated the line correctly but in the forgot to place pi with the volume of line and hence got wrong answer...so how many marks i ll get out 9..???????

 

[umer]

The exact answer was 11/12 pie...

11/12pie and 0.91pie is the same thing..
11/12pie=0.91pie

 

[umer]

hey tell me one thing...my volume under curve was correct...i.e.2pi...i integrated the line correctly but in the forgot to place pi with the volume of line and hence got wrong answer...so how many marks i ll get out 9..???????

I am sure u`l get more then 6

 

[MAVtKnmJ]

The exact answer was 11/12 pie...

11/12pie and 0.91pie is the same thing..
11/12pie=0.91pie

Not entirely correct, it depends on the accuracy demanded by the question. In any case 11/12 is not equal to 0.91 because when you round of 0.9166 to 3 sig figures (that's usually what you should write your final answer in unless stated otherwise) it becomes 0.917 or 0.92 (to 2 sig figures).

You can lose a mark for this so be careful in future :/

So the better answer in this case would be 11/12 pi unless the question demanded it in decimal form.

P.S

It's called "Pi" not "Pie" lol

 

[soumayya]

i was thinking of a delicious pie at that moment.....lol

 

[MAVtKnmJ]

You and probably the rest of them as well

 

[soumayya]

yh..lol

 

[Frooty]

DAMN :mrgreen:
i got volume under curve as 2pi
but for the line i used the trapezium :s i got so numb head tht i forgot i was to find the volume not area
well well .. kindly help me
we had to find cordinates of y axis in 1st part
i got (0,1) and ( 5, 0.5 )
is it correct??
please do reply

 

[soumayya]

i got the same coordinates...it has to be correct...because they satisfy the given equation of the line..