• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

Mathematics: Post your doubts here!

Messages
53
Reaction score
2
Points
18
It is because the shaded region is above the curve and if you try to find the volume directly by integrating square of given equation about x-axis it gives the volume of substance formed when the area bounded by the curve and x-axis (which is below the curve) is rotated about x-axis.
So first you have to rotate a rectangle formed by line AB with x-axis so that a cylinder is formed then find its volume and finally subtract the volume of curve rotated about x-axis which will give the volume of required region...
GOT IT????

Yes got it, thanks alot!
 
Messages
681
Reaction score
438
Points
73
Yeah, like mentioned above you just need to suggest a suitable value. There's a range of answers (like the mean being 40-80 kg and deviation being like 10 kg) so you don't really need to worry about it.
Thanks a lot !! :)
 
Messages
11
Reaction score
2
Points
13
Please solve this question , i tried it doing so many times but i am unable to get the same gradient ( as per marking scheme ) and equation required to be shown in part (i)
w0rhtx.png
 

Dug

Messages
227
Reaction score
515
Points
103
Please solve this question , i tried it doing so many times but i am unable to get the same gradient and equation required to be shown in part (i)
w0rhtx.png
AoA wr wb

First find the coordinates of A:
At A, y=0
2-(18/2x+3) = 0
u get x=3

Now find the derivative of the curve:
dy/dx = -18(2x+3)^-1-1 (-1) (2)
dy/dx = 36/(2x+3)^2

At A, x=3
dy/dx = 36/(2(3)+3)^2 = 4/9

For the line AC:
m= -9/4
Insert coordinates of A
0 = -9/4 (3) +c
c=27/4
y=(-9/4)x +27/4
4y+9x=27

No need of thanks but I need prayers. ;)
 
Messages
2,211
Reaction score
1,261
Points
173
how to sketch the graph of 5-3sin2x ????????? (0<=x<=pi)
does it have an inverse?
 
Messages
138
Reaction score
19
Points
28
Please solve this question , i tried it doing so many times but i am unable to get the same gradient ( as per marking scheme ) and equation required to be shown in part (i)
w0rhtx.png

(i)
y=2-18/(2x+3)
find the value of x when y=0
0=2-18/(x+3)
x=3 So,Coordinates of A (3,0)

find y' it would be (16x-21)/(2x+3)^2
find y' at A = put 3 in place of x in above equation :
=4/9
as m1*m2=-1
so gradient of normal (AC) will be -9/4

Equation of AC:
(y-y1)=m(x-x1)
use A (3,0) and m=-9/4
y-0=(-9/4)(x-3)
4y=-9x+27
4y+9x=27 Done Hope u got it :)
 
Messages
11
Reaction score
2
Points
13
AoA wr wb

First find the coordinates of A:
At A, y=0
2-(18/2x+3) = 0
u get x=3

Now find the derivative of the curve:
dy/dx = -18(2x+3)^-1-1 (-1) (2)
dy/dx = 36/(2x+3)^2

At A, x=3
dy/dx = 36/(2(3)+3)^2 = 4/9

For the line AC:
m= -9/4
Insert coordinates of A
0 = -9/4 (3) +c
c=27/4
y=(-9/4)x +27/4
4y+9x=27

No need of thanks but I need prayers. ;)

thanks buddy btw even i was doing it the same way but you see when i was solving it the answer was coming to 0.444 as i have a MS calculator and when i was checked now with ab/c i could see it means the same as 4/9 :p i guess i need to get myself an ES calculator now or get used to using the ab/c button more often :p anyways thanks man (despite you mentioned it but i should say this as you helped me freakout less and helped me figure out the problem :) and well sure i pray for your success :) best of luck (y)
 
  • Like
Reactions: Dug

Dug

Messages
227
Reaction score
515
Points
103
how to sketch the graph of 5-3sin2x ????????? (0<=x<=pi)
does it have an inverse?
Y-intercept = 5
Amplitude = 3
The function is reflected in x-axis (inverted) because of the negative sign.
cycles = 2

If the domain was 0 <=x <= 2pi then you would have to fit 2 inverted sine cycles in that period. But its not...u just have to construct an inverted sine graph in the stated domain.

And prayers needed!!! :p
 
Messages
2,211
Reaction score
1,261
Points
173
Y-intercept = 5
Amplitude = 3
The function is reflected in x-axis (inverted) because of the negative sign.
cycles = 2

If the domain was 0 <=x <= 2pi then you would have to fit 2 inverted sine cycles in that period. But its not...u just have to construct an inverted sine graph in the stated domain.

And prayers needed!!! :p

tnx a lot
sure :)
 
  • Like
Reactions: Dug
Top