tan ( pi/2 ) in objective-c (math.h) not undefined

Question

I wrote this test code:

NSLog(@"%g", tan(M_PI / 2.0));

and the output of the console is:

1.63312e+16

The issues is about approximation, right? Did I make some mistakes or the tan function of math.h really doesn't handle this case itself (returning me INFINITY) ? shall I handle theese input cases myself (example: when I get pi/2 input value I return an error message) or is there a better (more elegant) way to get the correct value ?

Thanks

Answer 1

Its because M_PI != real pi because it cannot be represented, so what you get from M_PI is approximation of pi, which its tangent is what you get.
Edit: the following:

printf("cos(M_PI / 2) = %.30f\nsin(M_PI / 2) = %.30f\n",
       cos(M_PI / 2), sin(M_PI / 2));

will print

cos(M_PI / 2) = 0.000000000000000061232339957368
sin(M_PI / 2) = 1.000000000000000000000000000000

Which shows cos(pi / 2) is non-zero.
Doing the division will give

1.63312393531953E16

which is exactly what you get.