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acos (Read 340 times)
arta
acos
Mar 31st, 2009, 6:34am  
hi can anyone help me with this problem, i am trying to use the formula
cos(J) = (sq (p) + sq (q) - sq (n))- 2*p*q;

so inorder to get J i need to use an acos like this ;

float J = acos((sq (p) + sq (q) - sq (n))- 2*p*q);
however when i println it says NaN

does anyone know what im doing wrong?
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TVS
Re: acos
Reply #1 - Mar 31st, 2009, 7:45am  
I think you have to look into the fact if you input radians or degrees into the acos() function.

When reading the Reference about acos(), it is said:
"This function expects the values in the range of -1 to 1 and values are returned in the range 0 to PI (3.1415927)."

So the value of 'value' (in the code below) has to be within -1 and 1, for acos() to work. This depends on the values of p,q and n...

Code:

float value = radians ((sq(p) + sq(q) - sq(n)) - (2*p*q));
float J = acos( value );

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