# C program for Sine Series

Before going to the program for Sine Series first let us understand what is a Sine Series?

Sine Series:

Sine Series is a series which is used to find the value of Sin(x).

where, x is the angle in degree which is converted to Radian.

The formula used to express the Sin(x) as Sine Series is

Expanding the above notation, the formula of Sine Series is

For example,

Let the value of x be 30.

So, Radian value for 30 degree is 0.52359.

So, the value of Sin(30) is 0.5.

## Program code for Sine Series in C:

```#include<stdio.h>
#include<conio.h>

void main()
{
int i, n;
float x, sum, t;
clrscr();

printf(" Enter the value for x : ");
scanf("%f",&x);

printf(" Enter the value for n : ");
scanf("%d",&n);

x=x*3.14159/180;
t=x;
sum=x;

/* Loop to calculate the value of Sine */
for(i=1;i<=n;i++)
{
t=(t*(-1)*x*x)/(2*i*(2*i+1));
sum=sum+t;
}

printf(" The value of Sin(%f) = %.4f",x,sum);
getch();
}
```

Related: C program for Cosine Series

## Working:

• First the computer reads the value of  ‘x’ and ‘n’ from the user.
• Then ‘x’ is converted to radian value.
• Then using for loop the value of Sin(x) is calculate.
• Finally the value of Sin(x) is printed.

Related: C program for Exponential Series

## Step by Step working of the above Program Code:

Let us assume that the user enters the value of ‘x’ as 45 and ‘n’ as 4.

1. Converting ‘x’ to radian value

x = x * 3.14159 / 180    (x = 45 * 3.14159 / 180)    So,  x=0.785398

1. It assigns t=x and sum=x (i.e. t=0.785398 and sum=0.785398)
2. It assigns the value of i=1 and the loop continues till the condition of the for loop is true.

3.1.   i<=n    (1<=4)    for loop condition is true

t = (0.785398 * (-1) * 0.785398 * 0.785398)/(2 * 1 * (2 * 1 + 1))

So,  t = – 0.08074

sum = 0.785398 + (- 0.08074)

So,  sum=0.70465

i++

So,  i=2

3.2.   i<=n    (2<=4)    for loop condition is true

t = (- 0.08074 * (-1) * 0.785398 * 0.785398)/(2 * 2 * (2 * 2 + 1))

So,  t = 0.00249

sum = 0.70465 + 0.00249

So,  sum=0.70714

i++

So,  i=3

3.3.   i<=n    (3<=4)    for loop condition is true

t = (0.00249 * (-1) * 0.785398 * 0.785398)/(2 * 3 * (2 * 3 + 1))

So,  t = – 0.000032

sum = 0.70714 + (- 0.000032)

So,  sum=0.707108

i++

So,  i=4

3.4.   i<=n    (4<=4)    for loop condition is true

t = (- 0.000032 * (-1) * 0.785398 * 0.785398)/(2 * 4 * (2 * 4 + 1))

So,  t = 0.000000274

sum = 0.707108 + 0.000000274

So,  sum=0.707108274

i++

So,  i=5

3.5.  i<=n    (5<=4)    for loop condition is false

It comes out of the for loop.

1. Finally it prints The value of  Sin(0.785398) = 0.7071
1. Thus program execution is completed.

## Output:

### 14 Responses

1. sahil says:

why didn’t we use -1.0 instead of pow((double)(-1),(double)(2*i-1))

• devang says:

Hi Sahil, We can use -1.0 instead of pow((double)(-1),(double)(2*i-1)). I have tired it and it works.
Also thanks for asking such a good question..

• Aman says:

Bro how to replace -1.0 pls provide a brief code.

• devang says:

Hi Aman, I have already updated the program and the code given above is the actual code.

2. Rex says:

can you put the C++ program for the same question?
it would really help me if you do.

3. kuldeep says:

Very good

• devang says:

Thank you kuldeep.. 🙂

4. Amso says:

Very consistent, clear and basic explaination so that everyone can understand without much effort.

5. Irf says:

Amazing explanation!

6. naveen says:

amazing explanation

7. Falit kumar says:

Amazing

8. Joshna says:

Is very good