Mathematics: Post your doubts here!

[Hamnah Zahoor]

hellodjfos;s'ff Can you please give me a rough idea of what is coding while calculating mean and standard deviation.

 

[hellodjfos;s'ff]

hellodjfos;s'ff Can you please give me a rough idea of what is coding while calculating mean and standard deviation.

Σ(x) would be the sum of all values in a data set. Σ(x-a) would mean that a is subtracted from every value in the data set for example I have a data set of 70 80 90 100... the Σ(x) is 340 but Σ(x-10) would be 10 subtracted from every value. We could manually calculate this but that would be very time-consuming and questions often dont tell us all the values in a data set. So we can use a formula of coding(which is given to us in the formula sheet):
Mean=Σ(x-a)/n +a..... so I'll use the values I used above to prove this ok. The mean of those values is 85, n is 4 and I am trying to find Σ(x-10), so I use this formula.
85=Σ(x-10)/4 +10.... Σ(x-10) turns out to be 300. You can now also try to subtract 10 from each value in the data set and find their sum and you would get the same answer.

The other formula used in coding(also mentioned in formula sheet) is:
Variance=Σ(x-a)^2/n - (Σ(x-a)/n)^2.... this is similar to the formula of finding variance itself. The concept around this can only be understood once you attempt questions.

 

[Ebrahim12]

Alright and will division do the reverse? And what if it is multiplied by a complex number?

Yes division is the opposite, you get these from the arg(az) = arg(z) + arg(z) and Re(az) = Re(a)*Re(z) rules. For complex numbers you have to work it out using these rules I think.

 

[Hamnah Zahoor]

Σ(x) would be the sum of all values in a data set. Σ(x-a) would mean that a is subtracted from every value in the data set for example I have a data set of 70 80 90 100... the Σ(x) is 340 but Σ(x-10) would be 10 subtracted from every value. We could manually calculate this but that would be very time-consuming and questions often dont tell us all the values in a data set. So we can use a formula of coding(which is given to us in the formula sheet):
Mean=Σ(x-a)/n +a..... so I'll use the values I used above to prove this ok. The mean of those values is 85, n is 4 and I am trying to find Σ(x-10), so I use this formula.
85=Σ(x-10)/4 +10.... Σ(x-10) turns out to be 300. You can now also try to subtract 10 from each value in the data set and find their sum and you would get the same answer.

The other formula used in coding(also mentioned in formula sheet) is:
Variance=Σ(x-a)^2/n - (Σ(x-a)/n)^2.... this is similar to the formula of finding variance itself. The concept around this can only be understood once you attempt questions.

Thank you

 

[A*****]

Yes division is the opposite, you get these from the arg(az) = arg(z) + arg(z) and Re(az) = Re(a)*Re(z) rules. For complex numbers you have to work it out using these rules I think.

Thanks man!

 

[MShaheerUddin]

Can anyone tell me:
In mechanics paper, when we integrate an expression, when should we have to find C as well..? In many questions, sometimes it requires c and sometimes it does not.
How can you judge that you have to find C.

 

[Ebrahim12]

Can anyone tell me:
In mechanics paper, when we integrate an expression, when should we have to find C as well..? In many questions, sometimes it requires c and sometimes it does not.
How can you judge that you have to find C.

You always add C when integrating and solve for it, its just that sometimes C equals zero.

 

[A*****]

You always add C when integrating and solve for it, its just that sometimes C equals zero.

And sometimes obviously you've got the limits so c is not needed

 

[Shemyaa]

Did anyone solve P1 paper? Or did you find the ms?
And question: Do Feb/March papers give an idea about May/June session paper? Because the paper was really easy and I don't think that's how it'll go this year.
I think stats will be tricky this year,

 

[Shemyaa]

PURE MATHS 1 FEB/MARCH ANSWERS (MINE)
1) P=6
2) f(x)=2/9x^3-x^2+2
3)118 cm^2
4)dy/dx=-2(2x-1)^-2 +2
d^2y/dx^2=8(2x-1)^-3
5) x=8 in minimum and x=1 is the maximum
6) a) q= 2 or -11/3 b) 130.7
7) b) p=8 and n=42
8) 54.8 and 125.3 b)sq root 3 +tan (2x)
9) a) k=2 b) f inverse is 2- square root (x-3) and domain is f(x) >4 c) gf(x) range is < or equal to 1/3 (I confused the most here tho)
10) 117pi/4 b) (0,78/11)
11)a)8 square root 2, b) T(4,8)
Please share your answers if you solved,

 

[A*****]

PURE MATHS 1 FEB/MARCH ANSWERS (MINE)
1) P=6
2) f(x)=2/9x^3-x^2+2
3)118 cm^2
4)dy/dx=-2(2x-1)^-2 +2
d^2y/dx^2=8(2x-1)^-3
5) x=8 in minimum and x=1 is the maximum
6) a) q= 2 or -11/3 b) 130.7
7) b) p=8 and n=42
8) 54.8 and 125.3 b)sq root 3 +tan (2x)
9) a) k=2 b) f inverse is 2- square root (x-3) and domain is f(x) >4 c) gf(x) range is < or equal to 1/3 (I confused the most here tho)
10) 117pi/4 b) (0,78/11)
11)a)8 square root 2, b) T(4,8)
Please share your answers if you solved,

I'll solve it tomorrow and get back to u!

 

[A*****]

View attachment 64668
I did it this way in 7iii, can you explain how did you get 5880?

First consider the situation if the letter A is in between...MAM would be 1 object and these 3 letters can't switch positions so that would be 7!/2!= 2520
If it's some other letter then there'd be 4 options for the middle letter so no. of arrangements would be 4x 7!/3!= 3360
Adding both gives 5880

 

[Shemyaa]

First consider the situation if the letter A is in between...MAM would be 1 object and these 3 letters can't switch positions so that would be 7!/2!= 2520
If it's some other letter then there'd be 4 options for the middle letter so no. of arrangements would be 4x 7!/3!= 3360
Adding both gives 5880

Thank youu

 

[mittul8yu98]

Does any one have statistics 2 notes
I have even started preparing
please help

 

[Shemyaa]

Does any one have statistics 2 notes
I have even started preparing
please help

I dont take S2 but look into this link
https://www.physicsandmathstutor.com/a-level-maths-papers/

 

[mittul8yu98]

I dont take S2 but look into this link
https://www.physicsandmathstutor.com/a-level-maths-papers/

thanks a lot

 

[student3737]

Hey guys are we supposed to know the large data set for edexcel? It’s a huge list, and our teachers never specified , she would just give us the data set in mocks

 

[Mushraf altaf]

ill appreciate help with this one,

 

[A*****]

PURE MATHS 1 FEB/MARCH ANSWERS (MINE)
1) P=6
2) f(x)=2/9x^3-x^2+2
3)118 cm^2
4)dy/dx=-2(2x-1)^-2 +2
d^2y/dx^2=8(2x-1)^-3
5) x=8 in minimum and x=1 is the maximum
6) a) q= 2 or -11/3 b) 130.7
7) b) p=8 and n=42
8) 54.8 and 125.3 b)sq root 3 +tan (2x)
9) a) k=2 b) f inverse is 2- square root (x-3) and domain is f(x) >4 c) gf(x) range is < or equal to 1/3 (I confused the most here tho)
10) 117pi/4 b) (0,78/11)
11)a)8 square root 2, b) T(4,8)
Please share your answers if you solved,

I think you've confused some numbering.....
I've got some different answers.
For 4 ii) x= 0 max and x=1 min
One of the angles in 7 a) is 54.7° not 54.8° according to me...a little difference though but the answer mark will be lost
For 7 b) my a is same but the value of b is -4
For 8 iv) my range is 0<gf(x)<1
And plz tell me the ans of the very last part i.e. 10 iii) mine is (4.5, 7.5)

 

[Shemyaa]

I think you've confused some numbering.....
I've got some different answers.
For 4 ii) x= 0 max and x=1 min
One of the angles in 7 a) is 54.7° not 54.8° according to me...a little difference though but the answer mark will be lost
For 7 b) my a is same but the value of b is -4
For 8 iv) my range is 0<gf(x)<1
And plz tell me the ans of the very last part i.e. 10 iii) mine is (4.5, 7.5)

4) I wrote an 8 instead of 0 by mistake so I took the wrong values, yes your answer is correct.
7) I think I got it 54.8 roundings it to 3sf but I really don't remember tbh,
and I got b=2 If you actually try -4 you'll get y=0, but I think you took 2/3pi which is wrong because t (in my pic) value has to be on the negative side so you should take -pie/3 (you're not shifting it towards left or right ), maybe they'll accept -4 but its not in the domain range they've given us.
8) for iv I confused somewhere I understood the range of f(x) has to be greater than 1 but I can't figure how to progress so please help
and 10)iii yes its (9/2, 15/2) sorry I messed up the order