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Nehal Samee
Nehal Samee

Reputation: 166

Confusing result while converting degree into radian in C

  int x;
  scanf("%d",&x);
  x=(double)((x*3.14)/180);
  printf("%.6lf",x);

When I run the above code and input x=60, I get -0.000000. 

  int x;
  double a;
  scanf("%d",&x);
  a=(x*3.14)/180;
  printf("%.6lf",a);

But when I run this above code, I get the correct answer.

I want to know where I am doing wrong. Is there problem in my type casting or use of double or any other thing? Any help will be appreciated. Thanks!

N.B. : I need to print output upto 6 digits after decimal.

Upvotes: 0

Views: 84

Answers (1)

Jabberwocky
Jabberwocky

Reputation: 50775

There are two problems in your code:

x = (double)((x*3.14)/180);

(x*3.14)/180 is already a double therefore this line is equivalent to:

x = (x*3.14)/180;

but anyway the type of x remains int, so if x was e.g 300, the new values of x will be 300 * 3.14/180 = 5.2333 which will be trunacated to 5.

The second problem is here:

printf("%.6lf",x);

As explained before, the type of x is int, but the "%.6lf" format specifier requires a double. If the variable types don't match the format specifier, the behaviour is undefined.

The second version of your code is perfectly correct, but be aware that the user can only enter integer values.

BTW: 3.14 is a very poor approximation of PI, I'm sure you can do better.

Upvotes: 5

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