Fear of flying persistent fear or anxiety when they consider flying, as well as during flying. They will avoid flying if they can, and the fear, anxiety, and avoidance cause significant distress and impair their ability to function. Take-off, bad weather, and turbulence appear to be the most anxiety provoking aspects of flying. The most extreme manifestations can include panic attacks or vomiting at the mere sight or mention of an aircraft or air travel. Around 60% of people with fear of flying report having some other anxiety disorder. The causes of flight phobia and the mechanisms by which it is maintained were
Rational function the degree of formula_29 and both are real polynomials. The rational function is not defined at It is asymptotic to formula_32 as formula_33 The rational function is defined for all real numbers, but not for all complex numbers, since if "x" were a square root of formula_35 (i.e. the imaginary unit or its negative), then formal evaluation would lead to division by zero: which is undefined. A constant function such as "f"("x") = π is a rational function since constants are polynomials. Note that the function itself is rational, even though the value of "f"("x") is irrational for all "x".