Rounding value and storing that value to variable

[rapidxone]

Hi folks! long time lurker here and decided to register since I couldn't find the answer to this.

Im having problems with something. I want to be able to round off a value to 1 decimal place and then store that value so that I can use it for cmath to use the tan( ) function.

Here's a sample code that I just wrote, sorry if there are any syntax errors.

#include <iostream>
#include <cmath>
using namespace std;

int main()
{
 double X1, X2
 const double Pi = 3.1459

 cout << "Enter the value: ";
 cin >> X1;
 
 X2 = (X1 * Pi)/180;

 cout << "The tangent is: " <<setprecision(4) <<fixed << tan(X2);

Basically I need to round off the X1 value that the user inputted and calculate the rounded value to convert that to radians so that I can use the tan function.

Any help is greatly appreciated.

[keineahnung]

Hi
Sorry I'm maybe being obtuse but why would you want to round off the value of X1 in the first place? Isn't that just going to give you a less accurate result?

[rapidxone]

Yes it would be a less accurate result but I want to either round up or down so that I can print a table of tangents that I can start in. For example 38.69 will round to 38.70, I would take that value as my starting value convert it to radians and print the tan, next I would do 37.71, then 37.72, 37.73,.....

Thanks

[keineahnung]

Try this link. There's some source code which I think would do what you're after:
http://www.cplusplus.com/forum/general/4011/
Regards, keineahnung

[freddy92]

Not really related, but your value of Pi is wrong. It's 3.14159, not 3.1459.

[rapidxone]

Will look at that link a little later.

thanks for the clarification of Pi freddy91lol i meant 92 =)

But does anyone else have a solution to this?

[keineahnung]

@rapidxone
Will look at that link a little later.

Well, if you looked at it first, you'd see there's a snippet of source code that does exactly what you want, so then there wouldn't be any need for anyone else to post a solution ;)

Anushi (5) Oct 7, 2008 at 9:11am
@buffbill
i m sorry but thr is a slight flaw in the code u gave.
for a number say 7.13, it'll return 7.2 instead of 7.1.so i propose a correction in ur code.

float rndup(float n)//round up a float type and show one decimal place
{
      float t;
      t=n-floor(n);
      if (t>=0.5)    
      {
              n*=10;//where n is the multi-decimal float
              ceil(n);
              n/=10;
              }
      else 
      {
              n*=10;//where n is the multi-decimal float
              floor(n);
              n/=10;
              }
      return n;
}          

floor() and ceil() both are defined in <cmath>

[rapidxone]

Thanks Keineahnung, I did look at the code and tried to see if that would work and my program just hangs. I made sure to change the variables as well.

I ended up finding a solution which worked for me.

When I call the Min_Angle_Rounded it shows up either rounded up or down depending on the value I inputed. I don't know if I have to do an If statement since whenever I put a value of 38.68 it rounds to 38.7 and when I put a value of 30.43 it rounds to 30.4 which is what I need.

Do you think I would need an If statement?