Author Topic: need help in C3  (Read 961 times)

Offline T.Q

  • SF Master
  • ******
  • Posts: 1557
  • Reputation: 5081
  • Gender: Male
need help in C3
« on: January 17, 2010, 08:36:05 am »
Given that x = 4 sin (2y + 6), find dy/dx in terms of x.

my answer to the Q was  dy/dx= 1/8cos(2y+6)     
but i didnt know how to write it in term of x can someone help me plz
No Matter What Happens In Life , Just Don't Lose Hope :)

Offline XFlufferzX

  • Newbie
  • *
  • Posts: 36
  • Reputation: 64
  • Gender: Female
Re: need help in C3
« Reply #1 on: January 17, 2010, 04:56:46 pm »
x = 4 sin (2y + 6)

Sin (2y +6) = x/4

where x = opp.
         4 = hyp.
To find adjacent uuse Pythagoras theorem

adj = sqrt 16 - x^2

Cos ( 2y +6) = adj / hyp
                  = (sqrt. 16 - x^2)/4

dy/dx = 1/8cos(2y+6)
Simplify

1/8 . 1/cos(2y+6)

1/8 . 1/ sqrt. 16 - x^2 / 4

= 1/2 sqrt 16 - x^2

eh If yuh couldnt understand wat I did let me know
check da attached paper
« Last Edit: January 17, 2010, 05:45:14 pm by XFlufferzX »
Success is a journey, not a destination.

Offline T.Q

  • SF Master
  • ******
  • Posts: 1557
  • Reputation: 5081
  • Gender: Male
Re: need help in C3
« Reply #2 on: January 17, 2010, 05:23:55 pm »
thank you:)
No Matter What Happens In Life , Just Don't Lose Hope :)

Offline astarmathsandphysics

  • SF Overlord
  • *********
  • Posts: 11271
  • Reputation: 65534
  • Gender: Male
  • Free the exam papers!
Re: need help in C3
« Reply #3 on: January 17, 2010, 07:31:10 pm »
See this for implicit differentiation

http://www.astarmathsandphysics.com/a_level_maths_notes/C3/a_level_maths_notes_c3_implicit_differentiation.html

I am just about to finish the C3 notes. Start C4 tomorrow

Offline T.Q

  • SF Master
  • ******
  • Posts: 1557
  • Reputation: 5081
  • Gender: Male
Re: need help in C3
« Reply #4 on: January 17, 2010, 07:36:52 pm »
See this for implicit differentiation

http://www.astarmathsandphysics.com/a_level_maths_notes/C3/a_level_maths_notes_c3_implicit_differentiation.html

I am just about to finish the C3 notes. Start C4 tomorrow

thank you so much ,
very helpful
No Matter What Happens In Life , Just Don't Lose Hope :)