ios4 - Value of sine 180 is coming out as 1.22465e-16 -


i want implement sine , cosine calculator in ios4:

if([operation isequal:@"sin"]){     operand = (operand*m_pi/180.0);     operand=sin(operand); }

the code gives me correct answer values 0 through 90.

when give value of 180, 1.22465e-16 answer. expect zero.

where small difference come from?

this caused inability of binary number system represent pi.

one possible solution use symmetry of sin:

sindeg(x) = sindeg(180 - x)

(or alternatively):

sin(x) = sin(m_pi - x)

transforming angle range (-pi/2 : pi/2) reduces error of approximation.

basically:

if([operation isequal:@"sin"]){   operand = fmod(operand, 360);   if (operand > 270) operand -= 360;   else if (operand > 90) operand = 180 - operand;   operand=sin(operand*m_pi/180.0); }

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