`double hypot(double __x, double __y)`

The hypot() function returns *sqrt(__x*__x + __y*__y)*. This is the length of the hypotenuse of a right triangle with sides of length *__x* and *__y*, or the distance of the point (*__x*, *__y*) from the origin. Using this function instead of the direct formula is wise, since the error is much smaller. No underflow with small *__x* and *__y*. No overflow if result is in range.