Mathematics: Post your doubts here!

[Saad the Paki]

Because x = 2.5 is out of the domain of f(x).

Ummm but it is in the domain of g (x) why not consider that?

 

[Rizwan Javed]

Ummm but it is in the domain of g (x) why not consider that?

Actually the value of f(x) is to be put into the function g(x). If some value is not valid for f(x), it will not be considered.
The thing to note here is that the values of f(x) are the domain for g(x). Meaning that for finding gf(x), first the value of x will be put into f(x), then the resulting value of f(x) will be put into g(x) to calculate a value for gf(x). Got it?

 

[Saad the Paki]

Actually the value of f(x) is to be put into the function g(x). If some value is not valid for f(x), it will not be considered.
The thing to note here is that the values of f(x) are the domain for g(x). Meaning that for finding gf(x), first the value of x will be put into f(x), then the resulting value of f(x) will be put into g(x) to calculate a value for gf(x). Got it?

Ooh yeah got it thanks

 

[farhan141]

Okay forget modulus.
We wanna find the area of triangle, so we'll take AC as base. To find the distance AC, we can use the distance formula (from coordinate geometry) or simply think about it. The line is vertical, so we just need to find the difference in i components of A and C. You'll get 2*sqrt(2).

For the height part, we just measure the horizontal distance between B and A, which is simply the difference in x coordinates of them, or the difference in real part of the numbers. That gives you 5*sqrt(2). Hope that's clear.

Edit: since you know all the coordinates, you can also use the Shoelace Formula for finding its area.

So for y coordinates is it important to mention iota? Thanks a lot btw, got the rest.

View attachment 60023
Maybe spoiler buttons are getting annoying for some.

Why is cos^2x = 0 if dy/dx is 0 for stationary point?

 

[qwertypoiu]

So for y coordinates is it important to mention iota? Thanks a lot btw, got the rest.


Why is cos^2x = 0 if dy/dx is 0 for stationary point?

I'm not sure what exactly you mean by y-coordinate and "iota" part.

We want to make dy/dx zero. Setting cos^2(x) = 0 is a very convenient method of achieving this. This is because cos^2(x) was a factor of dy/dx. Hope that made sense.

 

[Maayee]

http://papers.gceguide.com/A Levels/Mathematics (9709)/9709_s14_qp_41.pdf
Can anyone help me with question 5 pls

 

[farhan141]

I'm not sure what exactly you mean by y-coordinate and "iota" part.

We want to make dy/dx zero. Setting cos^2(x) = 0 is a very convenient method of achieving this. This is because cos^2(x) was a factor of dy/dx. Hope that made sense.

U mentioned 2sqrt2i so I was asking is it important to mention i when calculating length of y axis?

Also i cant understand the cos^2 part. Cant u include the 4 with it? Is there any other way of solving it?

 

[qwertypoiu]

U mentioned 2sqrt2i so I was asking is it important to mention i when calculating length of y axis?

Also i cant understand the cos^2 part. Cant u include the 4 with it? Is there any other way of solving it?

Well if you make it clear that you are treating A and C as coordinates then I think there is no need to mention i. But if you are treating them as complex numbers and finding the modulus of the "complex number" AC, then you should mention i. The formula for modulus is |s| = sqrt(ss*)

As for your second question. Whenever you wanna solve any algebraic equation of the form f(x) = 0, and f(x) is given in factors, then you can set these factors as zero. This is because 0 multiplied by anything is equal to 0. For example:
(X-2)(X-3) = 0
So either (X-2)= 0 or (X-3) = 0
If there was a constant factor:
4(X-2)(X-3) = 0
We wouldn't say 4=0 because we know that's not true. We only take VARIABLE factors to be equal to zero if it is possible.
In your question we wanted to set dy/dx equal to zero, and cos^2(X) happened to be a factor of it. If a value of X is such that cos^2(X) = 0, then this guarantees that dy/dx is also equal to zero.

 

[mohmed ahmed soliman]

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help in 3 iii

i may fail in S1 i really need help

 

[Saad the Paki]

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help in B

i didnt understand the last step ofk ur asnwer
u found probabillity of being between 1.9-b and 1.9+b
then what should e do with 80%

I answered this question, there is no 1.9+b here

 

[Saad the Paki]

i may fail in S1 i really need help

You know I felt the same way when I started stats but I kept on doing papers and kept on getting bad marks.But then I felt confident after I had done about 10-15 papers
But if you just do the papers without understanding it isn't gonna help. Why don't you ask your teachers to explain your doubts to you I'm sure it will be much clearer to you then.

 

[mohmed ahmed soliman]

HELP IN III

 

[mohmed ahmed soliman]

You know I felt the same way when I started stats but I kept on doing papers and kept on getting bad marks.But then I felt confident after I had done about 10-15 papers
But if you just do the papers without understanding it isn't gonna help. Why don't you ask your teachers to explain your doubts to you I'm sure it will be much clearer to you then.

I DONT GO TO SCHOOL i stopped privates tution
why dont go to school well i dont have enough time so i am posting my qs hoping that someone will help and thanks for anyone who help

 

[mohmed ahmed soliman]

View attachment 59995
View attachment 59996
in I why o.256^4 why not 0.256*4
i cant do anything in II

help in II

 

[farhan141]

Well if you make it clear that you are treating A and C as coordinates then I think there is no need to mention i. But if you are treating them as complex numbers and finding the modulus of the "complex number" AC, then you should mention i. The formula for modulus is |s| = sqrt(ss*)

As for your second question. Whenever you wanna solve any algebraic equation of the form f(x) = 0, and f(x) is given in factors, then you can set these factors as zero. This is because 0 multiplied by anything is equal to 0. For example:
(X-2)(X-3) = 0
So either (X-2)= 0 or (X-3) = 0
If there was a constant factor:
4(X-2)(X-3) = 0
We wouldn't say 4=0 because we know that's not true. We only take VARIABLE factors to be equal to zero if it is possible.
In your question we wanted to set dy/dx equal to zero, and cos^2(X) happened to be a factor of it. If a value of X is such that cos^2(X) = 0, then this guarantees that dy/dx is also equal to zero.

Oh alright.

So we have to ignore the 4 that is being multiplied with cos^2x and the other function.

 

[farhan141]

The circled questions

 

[mohmed ahmed soliman]

I answered this question, there is no 1.9+b here

ok now i enderstood ur answer sorry

 

[mohmed ahmed soliman]

View attachment 59995
View attachment 59996
in I why o.256^4 why not 0.256*4
i cant do anything in II

help!

 

[Saad the Paki]

I DONT GO TO SCHOOL i stopped privates tution
why dont go to school well i dont have enough time so i am posting my qs hoping that someone will help and thanks for anyone who help

NO offence but the sort of questions you're asking are very basic which means you haven't quite understood the concept. So you need to do that first before doing past papers

 

[Eugene99]

i may fail in S1 i really need help

You need to plan and categorize your study.
The first thing is, your concept should be clear. You could take concepts from anywhere, be it notes, books or some youtube videos. Doing topic by topic helps a lot! For that, get topical past papers, they are life-savers! First revise a topic, (it's concepts), then do past papers on that topic. The first few questions seem daunting but as you go along, it gets easier. Because of doing topicals, you eventually find the pattern in the paper. Your mind accepts things more easily if they are categorized. So, when you start solving questions on a particular topic, there are like 20-25 questions on each topic in S1. As for me, when I reach the end, it gets so easier that it almost gets boring.
After you are done topic by topic, then try year by year. Though, there isn't much time but still, something is better than nothing. I finished my last topic yesterday and today I solved my first yearly S1 and believe me, my paper was 98% correct, and I did it in almost 1 hour.