1. ## 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?

2. use the acos() function

3. 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.

4. I use acos() but, it does not calculate properly

5. Are you assigning it to an integer variable? Make sure you're using a float.

6. Originally Posted by MyDestiny
I use acos() but, it does not calculate properly
Post the code.

7. what do u mean float?
i didn't assign it to anything

8. I keep getting...

-1.#IND

9. 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

All of the trig functions in <cmath> use radians, not degrees. Maybe that will help. (?)

11. 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;
}```

12. 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

13. I just wanted to let you all know that I figured out the answer... THANKS a bunch for your help!