# How do...

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• 02-09-2005
MyDestiny
How do...
How do you put in code on C++ [(cos^-1) which is found on calculators as shift cos]...

what I am trying to do is solve for theta...

cos (theta) = Fy/Fx

how would i put that in code?
• 02-09-2005
Salem
use the acos() function
• 02-09-2005
Kaelin
Do you have an IDE, like Borland CBuilder, MS Visual C++, or anything to that effect? If so, usually you can use the help function to search when you're just looking for a function.

Searching cos would probably yield acos as an alternate result.
• 02-09-2005
MyDestiny
I use acos() but, it does not calculate properly
• 02-09-2005
Kaelin
Are you assigning it to an integer variable? Make sure you're using a float.
• 02-09-2005
AH_Tze
Quote:

Originally Posted by MyDestiny
I use acos() but, it does not calculate properly

Post the code.
• 02-09-2005
MyDestiny
what do u mean float?
i didn't assign it to anything
• 02-09-2005
MyDestiny
I keep getting...

-1.#IND

as my answer
• 02-09-2005
Kaelin
What are you doing with it?

You either need to use it in an expression or assign it to a variable.

float accepts decimal values. Integers, as you know, cannot - int in C++ is the same as a real-life integer where no decimal values are allowed
• 02-09-2005
DougDbug
Radians?
All of the trig functions in <cmath> use radians, not degrees. Maybe that will help. (?)
• 02-09-2005
Salem
Example
Code:

```#include<stdio.h> #include<math.h> int main(){     double angle = 0.5; /* this is in radians */     double c = cos( angle );     double d = acos( c );     printf( "%f %f %f\n", angle, c, d );     return 0; }```
• 02-09-2005
Kaelin
Quote:

All of the trig functions in <cmath> use radians, not degrees. Maybe that will help. (?)
Exactly - I suspect this might be where the problem lies. Radians are ugly numbers, almost always involving a decimal point. Degrees are often the opposite - 270deg, 60 deg, 45 deg, etc.

I think MyDestiny might be using integer containers but it's hard to say without seeing the code
• 02-10-2005
MyDestiny
I just wanted to let you all know that I figured out the answer... THANKS a bunch for your help! :)