maths and functions

[akol ompen]

Morning I did two exercises and in both  i make some mistakes.I dont know what i did wrong.If something is missing or not .

first exercise

I have a = -1.5, b = 1.5, h = 0.1.We use this variables  x from a until b with "step" h (its a for loop ).After i have this [deleted link] and i will  printf the variables x,y.The program  will be finished when x is bigger than b.
what i did :
#include <std.h> #include <stdlib.h> #include <math.h> main(){ int a=-1.5; int b=1.5; double h=0.1; int x; int y; for(x=a;x<=b;x=x+h){ while(x<b){ if(abs(x)>1){ y=1/sqrt(pow(x,2)-1; printf("y= %d",y); else if(abs(x)==1){ y=-9999; printf("y= %d",y); }else if(abs(x)<1){ y=1/sqrt(1-pow(x,2)); printf("y= %d",y); } } system("Pause"); } }

first exercise
we read  x and n( the number of term will be used).We give 1 to the variable i.We give 1 in the variable term.We give the variable 1 to myexp.For each term i=1...n.we calculate each term from previous with the use of reduction type term<--term*x/i.We add the new term on myexp.We printf the x,myexp and exp(x).

what i did:
#include <stdlib.h> #include <math.h> int factorial(int n); main(){ int x; int n; int sum=1; int i=1; int myexp=1; for(i=1;i<=n;i++){ sum=pow(x,i)/ factorial(int i) my exp=myexp+sum; printf("my exp",myexp); } system("Pause"); } int factorial(int n){ int product=1; for(j=1;j<=n;j++){ product=product*i; return product; }

[Campbell Ritchie]

Please tell us the full details; we can only help if we know what is going wrong. What is supposed to happen and what does happen? I think I can see a compiler error somewhere. Add the image to the post, not the link (which I shall delete) because some people are reluctant to click such links. Please explain what the formula is supposed to calculate.

[Campbell Ritchie]

Please post the actual code with correct formatting (see suggestions here). You need to be able to read the code yourself, and incorrect indentation will stop you reading it. Go through the error messages from the compiler first. Why are you mixing int arithmetic and double arithmetic? Please explain what the loops mean.

[akol ompen]

Campbell Ritchie wrote:Please tell us the full details; we can only help if we know what is going wrong. What is supposed to happen and what does happen? I think I can see a compiler error somewhere. Add the image to the post, not the link (which I shall delete) because some people are reluctant to click such links. Please explain what the formula is supposed to calculate.

#include <stdio.h> #include <stdlib.h> #include <math.h> main(){ /* i give on variables numbers. */ double a=-1.5; double b=1.5; double h=0.1; int x; int y; /* a loop for .We use this variables  x from a until b with "step" h.I think its right the way i wrote it. */ for(x=a;x<=b;x=x+h){ /* the variable x if it is bigger than the b the program will be finished.Thats why i use a while loop */ while(x<b){ /* now if the absolute from  variable x is bigger from 1 then will be a new variable y (in the exercise has f(x)=y=...  , i just dont use the f(x) i hope i am not doing wrong.) . A new variable y that will have the number 1 divide the t root of the second exponential x and this will subtraction the number 1 .More detail 1 up down the root that inculde the exponential power 2 to x and the subraction with 1. I gave it as much as i could more understandable.After will show with the print f the result */ if(abs(x)>1){ y=1/sqrt(pow(x,2)-1); printf("y= %d",y); /* if the absolute x is equal to 1 then the new variable y will be show the result -9999 and the result will be printed */ }else if(abs(x)==1){ y=-9999; printf("y= %d",y); /* and the last case if the absolute x is smaller than 1 then it will be y the new variable that will have the 1 divide with the root of 1 substract the x exponential  power 2 /* }else if(abs(x)<1){ y=1/sqrt(1-pow(x,2)); printf("y= %d",y); } } i cant edit my code .I did something on it some changes.If i understand good i am not permited to put link (sorry i didnt knew that) and i tryed find how to put image from my pc to the post but i didnt managed to.In any case i will do again if i am somewhere false.Whats its going on this exercise is that it cant be run properly.What i mean is that on  dev-c++ i press up complile & run and it is doing a calculate 0y= that is never finished.What it should do is to show only some numbers.

[akol ompen]

Campbell Ritchie wrote:Please tell us the full details; we can only help if we know what is going wrong. What is supposed to happen and what does happen? I think I can see a compiler error somewhere. Add the image to the post, not the link (which I shall delete) because some people are reluctant to click such links. Please explain what the formula is supposed to calculate.

in the second exercise
#include <stdio.h> #include <stdlib.h> #include <math.h> /* its a method .I give name it factorial because thats what it is.I put it outside the main i delclare it there */ int factorial(int n); main(){ /* i give on variables numbers .I give the type int because thats it seems to be .Maybe the sum it could be double */ int x; int n; int sum; int j; int i=1; int myexp=1; /* i am doing a loop for.To count until n.Its a math symbol Sum with S caps lock . Up to this S it has n and down of S it has i=0.On the right of the number x and power i divide this i!.After =  1+ x/1!+x and in power 2 /2!+ x in power 3 /3!+...+x and in power n / n!. Its the type of a guy who started the name with M.Not Taylor series. i cant remember his name */ for(i=1;i<=n;i++){ /* what i am doing next is i  i use the variable sum to save the result of divide the x power to i with the method (which i name it factorial). */ sum=pow(x,i)/ factorial(int i); /* it says to add this on the variable myexp */ my exp=myexp+sum; /* i printf the myexp */ printf("my exp",myexp); } system("Pause"); } /* a method which is factorial .I did what it is on the math type and this i use it to divide with x^i . I dont know what i am doing wrong.This exercise is too difficult for me */ int factorial(int n){ int product=1; for(j=2;j<=n;j++){ product=product*i; return product; } system("Pause");
i dont think is right i think i have done mistakes. On dev-c++ i take this messages.Expected primary -expression before int.j not declared and i was not declared.Its too difficult this exercisee .I dont know what am i doing wrong

[Campbell Ritchie]

Let's stick to the first exercise. You have started by posting unformatted code which needs a lot of translation to make any sense of. Go and copy the code with indentation and spaces surrounding all binary operators. You need to be able to read your code more than I do.
Don't try to explain what is obvious, like having to declare the variables.
Go to line 20. Work out the values of b and x at the start of that loop. Where are those values changed? What will happen to the loop once you start running it?
Why are you using pow(x, 2)? I have already told you to use x * x instead.
Why are you mixing integer and floating‑point arithmetic? What happens if you try to assign a value with fractions to an integer?

[Campbell Ritchie]

Please read about abs(). Who told you to use it? It is not appropriate for the current application.
Please post the original image with the formula; I removed the link for reasons I explained earlier. I can see it, and I think it evaluates to
1.0 ÷ √(|x² − 1.0|)
in which case when x = ±1, the formula will evaluate to ∞.

What is it the formula for?

I haven't looked at the second exercise yet.

[akol ompen]

Campbell Ritchie wrote:Please read about abs(). Who told you to use it? It is not appropriate for the current application.
Please post the original image with the formula; I removed the link for reasons I explained earlier. I can see it, and I think it evaluates to
1.0 ÷ √(|x² − 1.0|)
in which case when x = ±1, the formula will evaluate to ∞.

What is it the formula for?

I haven't looked at the second exercise yet.

"indentation and spaces surrounding all binary operators" i didnt catch it.If you could do an example please.What i think you mean is that i do lines with out wrote something? .Next,I go to line 20 probably you reffer to  fro loop.The variable b is standar i think it doesnt change its b=1.5 the variable x is changing with x=x+h until this will be bigger than the number b.I used pow(x,2) because thats what they told me ,sorry i will fix it.My mistake I will doing it double.I dont know what will happen but its not good as far as i know and from java.Abs() is need on this exercise,why isnt appropriate?i think i should declare #define f(x) 1.0 ÷ √(|x² − 1.0|) but i am not sure about that.I agree 1.0 ÷ √(|x² − 1.0|) this is it  and that x = ±1.The formula is just an exercise to appear the  results of y .
#include <stdio.h> #include <stdlib.h> #include <math.h> main(){ double a=-1.5; double b=1.5; double h=0.1; double x; double y; for(x=a;x<=b;x=x+h){ while(x<b){ if(abs(x)>1){ y=1/sqrt(pow(x,2)-1); printf("y= %d",y); }else if(abs(x)==1){ y=-9999; printf("y= %d",y); }else if(abs(x)<1){ y=1/sqrt(1-pow(x,2)); printf("y= %d",y); } }

[Henry Wong]

akol ompen wrote:
"indentation and spaces surrounding all binary operators" i didnt catch it.If you could do an example please.What i think you mean is that i do lines with out wrote something?

Which is more readable? understandable?

This? ....

for(x=a;x<=b;x=x+h){ while(x<b){ if(abs(x)>1){ y=1/sqrt(pow(x,2)-1); printf("y= %d",y); }else if(abs(x)==1){ y=-9999; printf("y= %d",y); }else if(abs(x)<1){ y=1/sqrt(1-pow(x,2)); printf("y= %d",y); } }                        

Or this? ...

for(x=a;x<=b;x=x+h){    while(x<b){        if(abs(x)>1){            y=1/sqrt(pow(x,2)-1);            printf("y= %d",y);        } else if(abs(x)==1){            y=-9999;            printf("y= %d",y);        } else if(abs(x)<1){            y=1/sqrt(1-pow(x,2));            printf("y= %d",y);        }    } }  

Also, your eariler code had comments. Why did you remove them? Granted, they might not have been the best comments, but you could have improved them, than removing them completely.

Henry

[akol ompen]

Henry Wong wrote:

akol ompen wrote:
"indentation and spaces surrounding all binary operators" i didnt catch it.If you could do an example please.What i think you mean is that i do lines with out wrote something?

Which is more readable? understandable?

This? ....

for(x=a;x<=b;x=x+h){ while(x<b){ if(abs(x)>1){ y=1/sqrt(pow(x,2)-1); printf("y= %d",y); }else if(abs(x)==1){ y=-9999; printf("y= %d",y); }else if(abs(x)<1){ y=1/sqrt(1-pow(x,2)); printf("y= %d",y); } }                        

Or this? ...

for(x=a;x<=b;x=x+h){    while(x<b){        if(abs(x)>1){            y=1/sqrt(pow(x,2)-1);            printf("y= %d",y);        } else if(abs(x)==1){            y=-9999;            printf("y= %d",y);        } else if(abs(x)<1){            y=1/sqrt(1-pow(x,2));            printf("y= %d",y);        }    } }  

Also, your eariler code had comments. Why did you remove them? Granted, they might not have been the best comments, but you could have improved them, than removing them completely.

Henry

I understand! Thanks a lot now i catch it i will do it

[akol ompen]

akol ompen wrote:

Henry Wong wrote:

akol ompen wrote:
"indentation and spaces surrounding all binary operators" i didnt catch it.If you could do an example please.What i think you mean is that i do lines with out wrote something?

Which is more readable? understandable?

This? ....

for(x=a;x<=b;x=x+h){ while(x<b){ if(abs(x)>1){ y=1/sqrt(pow(x,2)-1); printf("y= %d",y); }else if(abs(x)==1){ y=-9999; printf("y= %d",y); }else if(abs(x)<1){ y=1/sqrt(1-pow(x,2)); printf("y= %d",y); } }                        

Or this? ...

for(x=a;x<=b;x=x+h){    while(x<b){        if(abs(x)>1){            y=1/sqrt(pow(x,2)-1);            printf("y= %d",y);        } else if(abs(x)==1){            y=-9999;            printf("y= %d",y);        } else if(abs(x)<1){            y=1/sqrt(1-pow(x,2));            printf("y= %d",y);        }    } }  

Also, your eariler code had comments. Why did you remove them? Granted, they might not have been the best comments, but you could have improved them, than removing them completely.

Henry

I understand! Thanks a lot now i catch it i will do it
#include <stdio.h> #include <stdlib.h> #include <math.h>   main(){ /*   i give on variables numbers. */ double a=-1.5; double b=1.5; double h=0.1; int x; int y; /* a loop for .We use this variables  x from a until b with "step" h.I think its right the way i wrote it. */ for(x=a;x<=b;x=x+h){   /* the variable x if it is bigger than the b the program will be finished.Thats why i use a while loop */    while(x<b){ /* now if the absolute from  variable x is bigger from 1 then will be a new variable y (in the exercise has f(x)=y=...  , i just dont use the f(x) i hope i am not doing wrong.) . A new variable y that will have the number 1 divide the t root of the second exponential x and this will subtraction the number 1 .More detail 1 up down the root that inculde the exponential power 2 to x and the subraction with 1. I gave it as much as i could more understandable.After will show with the print f the result */           if(abs(x)>1){           y=1/sqrt(pow(x,2)-1);           printf("y= %d",y); /* if the absolute x is equal to 1 then the new variable y will be show the result -9999 and the result will be printed */           }else if(abs(x)==1){            y=-9999;            printf("y= %d",y); /* and the last case if the absolute x is smaller than 1 then it will be y the new variable that will have the 1 divide with the root of 1 substract the x exponential  power 2 /*           }else if(abs(x)<1){           y=1/sqrt(1-pow(x,2));           printf("y= %d",y);           }           } i will do and the next exercise after .Lets finish this.

[Campbell Ritchie]

Henry Wong wrote:. . . . Which is more readable? understandable?

I would have written this:-for (x = a; x <= b; x = x + h) {    while (x < b){        if (abs(x) > 1) {            y = 1 / sqrt(pow(x, 2) - 1);            printf("y =  %d", y);        } else if (abs(x) == 1) {            y = -9999;            printf("y = %d", y);        } else if (abs(x) < 1) {            y = 1 / sqrt(1 - pow(x, 2));            printf("y = %d", y);        }    } }As I explained earlier, that is not correct code, but at least formatted correctly. You need to use the formatting to make the code legible to yourself.