Chinese name
fulcrum
function
As a fixed point for support
definition
The fixed point around which the lever rotates.
multivalue function
w=f(z)
Physical nouns
A fixed point where a lever is used to support an object. Fulcrum o: the fixed point around which the lever rotates.
Mathematical term
Generally speaking, for a multivalued function w=f(z), if the function value w does not recover once near a certain point, and the function values of each single-valued branch are the same at that point, then it should be the fulcrum of the multivalued function.
If the function value w recovers when z circles around the fulcrum n times, the point is called n- 1 fulcrum of multivalued function.
For example, the function w=sqrt(z), obviously, the value of w will recover after two weeks around the fulcrum z=0 along the Z-L, so z=0 is the first-order fulcrum of w=sqrt(z). In addition to z=0, z=∞ is also the first-order fulcrum of w=sqrt(z).