Help with Sin in Taylor series!!!

[josh2two]

I can't figure out how to do the sin of a function using taylor series in c++.

I figured out the cos

for( i = 2; i <= 2 * N; i+= 2)
{
term = -1 * term * x* x / (i* (i-1));
sum = sum + term;
}


PLEASE help me find the sin formula.

[teknomage1]

These guys are always good for math quandaries. The def for sin is in the second equation block. http://mathworld.wolfram.com/TaylorSeries.html

[josh2two]

I know the equation for the sin in taylor series. My problem is putting it into my c++ program like i did with the cos.

this is the cos
for( i = 2; i <= 2 * N; i+= 2)
{
term = -1 * term * x* x / (i* (i-1));
sum = sum + term;
}


PLease help with the sin code of the taylor.

[teknomage1]

Okay... Sin doesn't seem any trickier than Cosine but here goes,

//Equation for Sin(x) 
//Sigma(0, infinity) { -1^n * (x^(2n+1))/(2n+1)! }  - Makes me wish vBulletin supported TeX

//Best to do things properly or not at all
int factorial (int n) {
     int i;
     int result = 1;
     if( n > 0 ) {
	  for( i = 1; i <= n; i++ ) {
	       result = result * i;
	  }
     }

     return result;
}

int taylor_sin (int pos, int x) {
     int i;
     int term;
     int sum = 0;
     
     for( i = 0; i < pos; i++ ) {
	  term = pow(-1, i) * pow(x,(2 * i + 1)) / factorial(2 * i + 1);
	  sum = sum + term;
     }
}

[josh2two]

im a begineer.

when i put that code into dev c++, i can't get it to work. It says something about the pow being the error.


thanks for your help
josh

[teknomage1]

It's from cmath

[josh2two]

i have the #include<cmath> already in the program.

please help

[teknomage1]

Quit being lazy. If you can't get the library function to work, write your own pow() function. Programming is about problem solving. Ideally, we want to avoid duplication but, the function isn't that hard to write.

int pow ( int base, int exp ) {
     if ( exp <= 0 ) {
	  //not mathematically correct but negative exponents won't return an int anyway
	  return 1; 
	       }
     else {
	  int i;
	  int result = 1;
	  
	  for( i = 0; i < exp; i++ ) {
	       result = result * base;
	  }

	  return result;
     }

[redhead]

Or link to the math library...

[Valmont]

#include <cmath>
{...
std::pow()
...}