C2 DOUBT edexcel

[halosh92]

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?

[astarmathsandphysics]

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.

[halosh92]

can u explain how they got the angle here on wat basis?

[halosh92]

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

[astarmathsandphysics]

When I get up

[halosh92]

could someone plz answer this question??

[astarmathsandphysics]

4 only include one or roots at 360, 0

[halosh92]

4 only include one or roots at 360, 0

i dont get why u chose such places to places the tan curve :S

[astarmathsandphysics]

They asked for answers in the range 0-360

[vanibharutham]

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

[halosh92]

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

[AS panic attack]

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

[halosh92]

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

[AS panic attack]

A=1, (5+or-sqrt 105)/8

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

Thanks

[Amr Fouad]

give me 2 mins