Author Topic: C2 DOUBT edexcel  (Read 2197 times)

Offline halosh92

  • SF Senior Citizen
  • *****
  • Posts: 730
  • Reputation: 1113
  • Gender: Female
    • meticulous-me
C2 DOUBT edexcel
« on: April 07, 2010, 08:02:40 pm »
A circle has the equation
x2 + y2 + 8x ? 4y + k = 0,
where k is a constant.
(a) Find the coordinates of the centre of the circle. (2)
Given that the x-axis is a tangent to the circle,
(b) find the value of k.

for part b...how to get the radius exactly?
everyday we wake up is a miracle, then how do we say miracles dont happen?????

Offline astarmathsandphysics

  • SF Overlord
  • *********
  • Posts: 11271
  • Reputation: 65534
  • Gender: Male
  • Free the exam papers!
Re: C2 DOUBT edexcel
« Reply #1 on: April 07, 2010, 11:41:59 pm »
Because the exapression completes the square as  (y+2)^2 it is two from the x acxis to the centre so the radius of the circle is 2.

Offline halosh92

  • SF Senior Citizen
  • *****
  • Posts: 730
  • Reputation: 1113
  • Gender: Female
    • meticulous-me
Re: C2 DOUBT edexcel
« Reply #2 on: April 08, 2010, 07:36:53 am »
can u explain how they got the angle here on wat basis?
everyday we wake up is a miracle, then how do we say miracles dont happen?????

Offline halosh92

  • SF Senior Citizen
  • *****
  • Posts: 730
  • Reputation: 1113
  • Gender: Female
    • meticulous-me
Re: C2 DOUBT edexcel
« Reply #3 on: April 08, 2010, 07:47:15 am »
Sketch on the same diagram the graphs of y = sin 2x and y = tan
2
x for x
in the interval 0 ? x ? 360°.
(b) Hence state how many solutions exist to the equation
sin 2x = tan
2
x ,
for x in the interval 0 ? x ? 360° and give a reason for your answer.

I have the answers i just need an explanation for part a
thx
everyday we wake up is a miracle, then how do we say miracles dont happen?????

Offline astarmathsandphysics

  • SF Overlord
  • *********
  • Posts: 11271
  • Reputation: 65534
  • Gender: Male
  • Free the exam papers!
Re: C2 DOUBT edexcel
« Reply #4 on: April 08, 2010, 08:14:13 am »
When I get up

Offline halosh92

  • SF Senior Citizen
  • *****
  • Posts: 730
  • Reputation: 1113
  • Gender: Female
    • meticulous-me
Re: C2 DOUBT edexcel
« Reply #5 on: April 08, 2010, 02:31:42 pm »
could someone plz answer this question?? :-\ ??? ??? ???
everyday we wake up is a miracle, then how do we say miracles dont happen?????

Offline astarmathsandphysics

  • SF Overlord
  • *********
  • Posts: 11271
  • Reputation: 65534
  • Gender: Male
  • Free the exam papers!
Re: C2 DOUBT edexcel
« Reply #6 on: April 08, 2010, 07:19:37 pm »
4 only include one or roots at 360, 0

Offline halosh92

  • SF Senior Citizen
  • *****
  • Posts: 730
  • Reputation: 1113
  • Gender: Female
    • meticulous-me
Re: C2 DOUBT edexcel
« Reply #7 on: April 09, 2010, 08:37:56 am »
4 only include one or roots at 360, 0
i dont get why u chose such places to places the tan curve :S
everyday we wake up is a miracle, then how do we say miracles dont happen?????

Offline astarmathsandphysics

  • SF Overlord
  • *********
  • Posts: 11271
  • Reputation: 65534
  • Gender: Male
  • Free the exam papers!
Re: C2 DOUBT edexcel
« Reply #8 on: April 09, 2010, 12:22:02 pm »
They asked for answers in the range 0-360

Offline vanibharutham

  • SF Citizen
  • ***
  • Posts: 169
  • Reputation: 749
  • Gender: Male
Re: C2 DOUBT edexcel
« Reply #9 on: April 11, 2010, 06:40:21 pm »
heres a way you can try

sin2x = tan2x
sin2x = sin2x / cos2x

sin2x cos2x = sin2x
sin2x cos2x - sin2x = 0
sin2x ( cos 2x - 1) = 0

sin 2x = 0 and cos 2x = 1

you come out with

x = 0, 90, 180, 270, 360
A genius is 1% intelligence, 99% effort.

Offline halosh92

  • SF Senior Citizen
  • *****
  • Posts: 730
  • Reputation: 1113
  • Gender: Female
    • meticulous-me
Re: C2 DOUBT edexcel
« Reply #10 on: April 15, 2010, 11:11:02 am »
a circle with centre O and radius 6 cm.
the  chord PQ divides the circle into a minor segemnt R1 of area A1
and  a major segment R2 of area A2. the chord PQ subtends an angle thita radians at O/
a) show that A1= 18 (thita- sin thita)
 given that A2= 3A1 and f(thita) = 2 thita - 2sin thita - pie
b) prove that f(thita)=0
c) evaluate f(2.3) and f(2.32) and deduce that 2.3<thita>2.32

how to do part b  and c
??
thxxx
everyday we wake up is a miracle, then how do we say miracles dont happen?????

Offline AS panic attack

  • Newbie
  • *
  • Posts: 28
  • Reputation: 49
Re: C2 DOUBT edexcel
« Reply #11 on: April 16, 2010, 12:24:15 pm »
can sme one solve this ques

the coefficient of x3 in the epansion of (2+x)(3-ax)4 is 30
find the values of the constant a.

please show step by step working
Thanks

Offline halosh92

  • SF Senior Citizen
  • *****
  • Posts: 730
  • Reputation: 1113
  • Gender: Female
    • meticulous-me
Re: C2 DOUBT edexcel
« Reply #12 on: April 16, 2010, 01:52:50 pm »
can sme one solve this ques

the coefficient of x3 in the epansion of (2+x)(3-ax)4 is 30
find the values of the constant a.

please show step by step working
Thanks

a=1
a= sqrt 30
 is this the answer? if not post the correct answer please :)
everyday we wake up is a miracle, then how do we say miracles dont happen?????

Offline AS panic attack

  • Newbie
  • *
  • Posts: 28
  • Reputation: 49
Re: C2 DOUBT edexcel
« Reply #13 on: April 16, 2010, 02:56:48 pm »
A=1, (5+or-sqrt 105)/8

please show workings i need to know how to get da ans

Thanks

Amr Fouad

  • Guest
Re: C2 DOUBT edexcel
« Reply #14 on: April 16, 2010, 03:25:19 pm »
give me 2 mins