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
Dirichlet eta function the formula_19 function is then analytic for formula_15, a region which includes the line formula_8. Now we can define correctly, where the denominators are not zero, or Since formula_24 is irrational, the denominators in the two definitions are not zero at the same time except for formula_25, and the formula_26 function is thus well defined and analytic for formula_15 except at formula_25. We finally get indirectly that formula_29 when formula_13: An elementary direct and formula_32-independent proof of the vanishing of the eta function at formula_13 was published by J. Sondow in 2003. It expresses the value of the eta function