Mathematics: Post your doubts here!

[anishh]

HELP NEEDED:600 rounds are fired from a gun at a horizontal target 50m long which extends from 950m to 1000m in range from gun.The trajectories of the rounds all lie in the vertical plane through the gun and the target.It is found that 27 rounds fall short of the target and 69 rounds fall beyond it.Assuming that the range of rounds is normally distributed,find the mean and standard deviation of the range.Estimate the number of rounds falling within 5m of the centre ot the target.

 

[WayneRooney10]

http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Mathematics%20(9709)/9709_w11_qp_11.pdf
Q4! Help needed quick.

Thanks!

 

[anishh]

i)at st pt,dy/dx(f"(x)=0
2x-6=0
x=3
ii)intergrate f"(x)=x^2-6x+c
when x=3,y=4
-4=(3)^2-6(3)+c
c=5
f(x)=x^2-6x+5
(N11 NO 4 P11)

 

[GriM ReapeR]

help solve: (x+3)^3+1=0

 

[WayneRooney10]

http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Mathematics%20(9709)/9709_w11_qp_31.pdf
Q4! Do explain every part of the working.

Thanks!

 

[AdeelRox]

(x+3)^3=-1
3lg(x+3)=lg(-1)
;no solution as lg(-1) is not valid

dude it would be
(x+3)^3 +1=0
x+3=(-1)^(1/3)
x+3=-1
x=-4

 

[Executor]

AOA,
Can anyone provide me the formula sheet for P1 and P3?
Thanks in advance.

 

[WayneRooney10]

3^x+2=3^x+3^2. Solve for x. And do tell me how you did it.

 

[AdeelRox]

3^x+2=3^x+3^2. Solve for x. And do tell me how you did it.

dude its simple
3^(x+2) = 3^(x+3)^2
since the base i.e 3 is same therefore cancelling base on both sides we have
x+2 = (x+3)^2
x+2 = x^2 + 6x + 9
x^2 + 5x + 7 = 0
applying formula, X= b^2 'plus minus' ((b^2 - 4ac)/2a)^0.5
X= -5/2 + (i(3)^(1/2))/2 , -5/2 - (i(3)^(1/2))/2
i hope this will help and wont get much complicated

 

[yashmehta96]

Please someone try this one from 9709/32/0/N/11
Question 10 part 2nd

 

[smzimran]

This is the solution to a question asked by bamteck:

Sorry for a v.late reply

Q7 :
(i) cut the triangle in half such that it becomes a right angled triangle

now
sin@ = (99/2) / r

r = 99 / 2sin@ ....eq(1)

Using the formula
s = r@
100 = r(2@)
100 = 2@r

Substitute eq(1) in above equation
100 = 2@ (99 / 2sin@)
100sin@ = 99@
sin@ = (99/100) @

so
sin x = (99/100) x

(ii) Find out the values of
sin x - (99/100) x

for values of x = 0.1 and x = 0.5
The change in sign shows that root lies in b/w

(iii) the equation from (1) was
sin x = (99/100) x

We have to process x = 50sin x - 48.5x to form above equation
x + 48.5x = 50sin x
49.5x = 50sinx

multiply both sides by 2
99x = 100sinx
(99/100) x = sin x

Shown

(iv) Simple .... just use the iteration formula

 

[smzimran]

Another question asked by bamteck

Q8 :

(i) let root(-3 + 4i) = a + bi
the squaring both sides
-3 + 4i = a^2 + 2abi + b^2i^2

Since i^2 = -1
(-3) + (4)i = (a^2 - b^2) + (2ab)i

Real part = Real part and Imaginary part = Imaginary part
a^2 - b^2 = -3 and 2ab = 4

Solve these equations simultaneously to get values of a and b

(ii) multiply z by (2 - i) / (2 - i) [compliment of denominator of z]

and use i^2 = -1

You will get the correct answer!

 

[smzimran]

Please someone try this one from 9709/32/0/N/11
Question 10 part 2nd

Search this thread i have done this question here before , around 14-15 may!

 

[Mithrandir]

PLEASE HELP!
Find the volume of the solid formed when area under the graph y=sec1/2x is rotated 360 degrees about the x-axis, for boundaries 0 to 1/3 pi (sorry, couldn't find the symbol)
AND...
Integrate the following function:
4x-18
4x^2 + 4x-3
THANKS
P.S. please show me the method behind this madness

 

[Amy Bloom]

Can somebody help me in Differential equations, i.e, how to separate the variables with illustrations please?

 

[bamteck]

URGENT ! Someone help me to solve out this.
Its from J03/P3
Thanks

 

[smzimran]

URGENT ! Someone help me to solve out this.
Its from J03/P3
Thanks

 

[smzimran]

Can somebody help me in Differential equations, i.e, how to separate the variables with illustrations please?

Simply take y variables to L.H.S and x variables to R.H.S
Let dy be on L.H.S and dx taken to R.H.S

It is better done in practise!

 

[smzimran]

PLEASE HELP!
Find the volume of the solid formed when area under the graph y=sec1/2x is rotated 360 degrees about the x-axis, for boundaries 0 to 1/3 pi (sorry, couldn't find the symbol)
AND...
Integrate the following function:
4x-18
4x^2 + 4x-3
THANKS
P.S. please show me the method behind this madness

For second question, factorise the denominator , break usiing partial fractions and then integrate , its not difficult, just lengthy!

 

[Amy Bloom]

Thanks a lot pal! Yet, i have difficuties when inversing etc.. if u know some examples which clearly supports what u said, please post them. tnx!

Simply take y variables to L.H.S and x variables to R.H.S
Let dy be on L.H.S and dx taken to R.H.S

It is better done in practise!