-1

This part of an app that I am working on, I have the following equation in objective C. All variables are floats. r is a sine of an angle and I would like to convert r to radians when diplayed in the text field.

```
r = ns/ni
r = sinf(r);
rr = asinf(r);
textfieldRi.text = [NSString stringwithFormat:@"%.02f", rr];
```

I am not getting correct results. Any suggestions please?

2

I'm not entirely certain what you think you're gaining by executing a sine followed by an inverse sine, except possibly to ensure the range of `r`

is reduced to it's smallest range, in which case `asin(sin(r))`

should work fine, assuming `r`

is already in radians.

If you want to convert `r`

to radians, I have to assume it's currently in degrees, in which case you just need to do something like:

```
radians = degrees * 3.141592653589 / 180.0; // or M_PI in math.h.
```

I would use M_PI instead of 3.14159 though.. - lnafziger 2012-04-04 05:41

Yeah, I never know whether ObjC has *all* the stuff that C has, so I was just playing it safe. If you *have* a PI constant, use that. Updated to incorporate the suggestion - paxdiablo 2012-04-04 05:44

Thank you for this advice worked - MacUser 2012-04-04 18:33

1

Objective-c automatically uses radians instead of degrees, however to convert degrees to radians divide by 180 then multiply by PI.

I m just starting to use the mathmatical function in objective C this is very important to know, thanks - MacUser 2012-04-04 18:35