Mathematics: Post your doubts here!

[The Sarcastic Retard]

I got two values of x. 1 is pi/6 and other is 5pi/6. I also found that pi/6 is maximum point, but i cant find 5pi/6 to be minimum point. Help required.



(iii) No idea. Help needed.

Thanks.

 

[The Sarcastic Retard]

As there is no one active in chemistry thread, I want someone to help me in this question(A2 - Electrochemistry chapter).
https://www.xtremepapers.com/commun...st-your-doubts-here.9859/page-748#post-948570
Thanks. ^_^

 

[Anum96]

View attachment 58135
I got two values of x. 1 is pi/6 and other is 5pi/6. I also found that pi/6 is maximum point, but i cant find 5pi/6 to be minimum point. Help required.


View attachment 58136
(iii) No idea. Help needed.

Thanks.

For a second, I doubted my eyesight. Very clear pictures I must say.
Lol, Wait up!

 

[Anum96]

Equation of the tangent
y = mx + c
c will be 0 since the tangent passes through origin.
gradient(Differentiate the equation of curve)
You will get e^x(3 -x)

Plug in the values.
y = mx + c [c = o & y = (4-x)e^x]
(4 - x)e^x = e^x(3 - x)x + 0
(4 - x)e^x = e^x(3 - x)x
e^x cancels out.
4-x = (3-x)x
4-x = 3x - x^2
4 - x - 3x + x^2 = 0
x^2 - 4x + 4 = 0
x(x-2) - 2(x-2) = 0
x or p is 2 Ans.

 

[The Sarcastic Retard]

Equation of the tangent
y = mx + c
c will be 0 since the tangent passes through origin.
gradient(Differentiate the equation of curve)
You will get e^x(3 -x)

Plug in the values.
y = mx + c [c = o & y = (4-x)e^x]
(4 - x)e^x = e^x(3 - x)x + 0
(4 - x)e^x = e^x(3 - x)x
e^x cancels out.
4-x = (3-x)x
4-x = 3x - x^2
4 - x - 3x + x^2 = 0
x^2 - 4x + 4 = 0
x(x-2) - 2(x-2) = 0
x or p is 2 Ans.

Thanks. Can u help me in other question as well.

 

[The Sarcastic Retard]

For a second, I doubted my eyesight. Very clear pictures I must say.
Lol, Wait up!

Ah. You are totally correct, they were clearest pictures I ever saw in my life. Thanks to GCE guide. (Y)

 

[Anum96]

Thanks. Can u help me in other question as well.

The other qs is so boring. :/
Lol, Wait

 

[Anum96]

Ah. You are totally correct, they were clearest pictures I ever saw in my life. Thanks to GCE guide. (Y)

Alright! Blame the innocent guide.

 

[The Sarcastic Retard]

The other qs is so boring. :/
Lol, Wait

Aha!! Waiting ^_^

 

[The Sarcastic Retard]

Alright! Blame the innocent guide.

Blame is on the correct thing They are innocent, but so naaughty.

 

[Anum96]

Aha!! Waiting ^_^

Look. You got the right answers and yes pi/6 is maximum. That means your working for derivative and double derivative is correct.
Second point is 5pi/6
Double derivative is -2cos(x)
Plug in the value. -2cos(5pi/6) [5pi/6 is 150]
Absolute value of cos 150 is -undrt3/2
Therefore -2(-undrt3/2) will give a positive value which comes out to be the minimum value of undrt3

 

[The Sarcastic Retard]

Look. You got the right answers and yes pi/6 is maximum. That means your working for derivative and double derivative is correct.
Second point is 5pi/6
Double derivative is -2cos(x)
Plug in the value. -2cos(5pi/6) [5pi/6 is 150]
Absolute value of cos 150 is -undrt3/2
Therefore -2(-undrt3/2) will give a positive value which comes out to be the minimum value of undrt3

I dont get

 

[Anum96]

I dont get

Use the same method you applied for first point. Plug in the value of x
If you dont remember the absolute value use your calculator. Pi is 180. So 5(180)/6 is 150
cos 150 is negative. And negative*negative gives out positive, And positive values are always minimum

 

[The Sarcastic Retard]

Use the same method you applied for first point. Plug in the value of x
If you dont remember the absolute value use your calculator. Pi is 180. So 5(180)/6 is 150
cos 150 is negative. And negative*negative gives out positive, And positive values are always minimum

ok thanks.

 

[Anum96]

ok thanks.

Welcome. Lol.

 

[The Sarcastic Retard]

Welcome. Lol.

can u help me in chem?

 

[Anum96]

can u help me in chem?

I don't take chemistry

 

[The Sarcastic Retard]

I don't take chemistry

Aha... Thanks a lot girl. ^^

 

[fleurisabelle]

badly stuck in Chain Rule...somebody help please
I know that dy/dx is gradient with respect to x but why the hell do they start using du/dx and d/dy, all of a sudden and what exactly does it mean?

 

[Anum96]

badly stuck in Chain Rule...somebody help please
I know that dy/dx is gradient with respect to x but why the hell do they start using du/dx and d/dy, all of a sudden and what exactly does it mean?

dy/dx is not just the gradient. It means differentiation of y with respect to x. Du/dx means differentiation of u with respect to x. In chain rule you have a fraction.
lets say
2x - 1
--------
3x

You usually assume numerator to be u and denominator to be v ( Its just the process of assigning variables )
and differentiate them separately.
u is 2x - 1
differentiating it will give you du/dx (its also written as u')as 2
v is 3x
differentiating it will give you dv/dx ( or v' ) as 3
Now you have these two answers just plug them in the chain rule formula which is given in your formula booklet.
( vu' - uv' )/ v^2
OR
v(du/dx) - u(dv/dx) / v^2

[(3x)(2) - (2x - 1)(3)] / (3x)^2