C3 and C4 DOUBTS HERE!!!

[The Golden Girl =D]

Give me a second ang3l

EDIT :

Using Quotient Rule , We differentiate :   { =>  Which is :  dy/dx = [ u'V - V'u ] / V² }

u = 5x² - 10x + 9  =>  u' = 10 x - 10

v = (x-1)² =>  v' = 2 (x-1)

dy/dx =>  [ { (10x-10) [ (x-1)² } - { 2 (x-1) [ 5x² - 10 x + 9] } ] /  [( x-1)⁴ ]

I took (x-1) as a Common factor so I got ;

dy/dx =>  (x-1) { [ (10x-10)(x-1) ] - [2(5x² - 10x + 9)] } / [ (x-1)⁴ ]

=> I cancelled out the (x-1) from the numerator and then expanded what is inside the brackets (numerator) and got the following :


dy/dx =>  [ 10x² - 20x +10 - 18 - 10x² + 20x] / [ ( x-1 )³ ]

since the 10x and -10x  , the 20x and -20x cancel out we have 10-18 = -8

So we get ;

dy/dx =>  -8 / [ (x-1 )³ ]

I hope I helped (:


Don't forget to include me in your prayers =D

[Malak]

Thanks GG

I have another doubt

Same paper c3 2005 June Q 5 part d (attached)

I get everything, except that in part d i am getting a negative answer for theta

for theta + 0.588 i get --> 0.429 and 0.5709..

and then for theta i get a negative answer :S

[The Golden Girl =D]

Since you knew how to solve the first part then I'll just go into the theta thing (:

the Equation you'll use is =>  sin theta [ squareroot52 sin (theta + 0.588)] =0 from part (c)

so sin theta = 0

we know that sin theta is 0 , at  pie and 2pie .... only 0 is accepted => check  the range

squareroot52 sin (theta + 0.588) = 0

theta + 0.588 = 0 , pie , 2 pie  (cuz I told you ,we know that sin theta is ZERO at these three angles )

so theta = pie - 0.588 = 2.553

theta =2pie -0.588 = 5.70  { rejected TOO big not within the range }


therefore Theta = 0 rad , 2.553 rad


This is one of the Tricks my teacher uses , I hope you got it (:

[I might have to go any minute cuz my bro's  got a project -.- ]

[Malak]

but isnt the range greater han 0 and less than pie then why do we consider 2 pie

[The Golden Girl =D]

I considered it but I  didn't put it in the final answer you see

[Malak]

I considered it but I  didn't put it in the final answer you see

you missed out 3 :S

Won't the equation be(x = theta) --> Sin x (4cosx + 6sinx -3) = 0

and later it will be Sinx [square root 52 sin(x + 0.588)] - 3 = 0

then, sin x = 0 and sqrt 52 sin(x + 0.588) - 3 = 0

[The Golden Girl =D]

Mr.Paul ,Can you please clear our doubt on this point =/

Thanks (:

[astarmathsandphysics]

happpy too. Entire question answered in attachment

[The Golden Girl =D]

May God bless you Sir ..Thanks (:

[Malak]

Umm >_< can you explain the last 2 lines, I don't get where did the 3.142 come from :S

And thankyou sir.

[astarmathsandphysics]

3.142 is pi!!!!!!!!!!!!

[Malak]

3.142 is pi!!!!!!!!!!!!

OMG *epic fail...*

Thanks again..

[-Cornea]

The chain rule used in differentiation is it a must to have two functions divided by each other so that  i can use it what i mean is i can deffrentiate (x+3)/(x+5) this using the rule  can i use the same way in deffrentiating  (1)/(x+4)

[Malak]

The chain rule used in differentiation is it a must to have two functions divided by each other so that  i can use it what i mean is i can deffrentiate (x+3)/(x+5) this using the rule  can i use the same way in deffrentiating  (1)/(x+4)

I guess you meant the quotient rule.
Yes, i guess you can use it for the 2nd equation as well..but that isnt the best way. You can simply bring the (x + 4) up as (x+4)^-1 and solve it using the chain rule

[-Cornea]

yeah i don't their names :p anyway thanks