For example, ∮ F DSL (F is a vector function and l is its integral path (it is a closed curve). Ds represents the differential of its integral path, and it is also the product of the vector f ds = FX * DX+FY * Dyf = FXI+FYJ (Ij is the unit vector on the xy axis).
Common symbols
Such as plus sign (+), minus sign (-), multiplication sign (× or), division sign (÷ or/), union of two sets (∩), intersection (∩), root sign (∩ ~), logarithm (log, lg, ln,