github.com/jingcheng-WU/gonum@v0.9.1-0.20210323123734-f1a2a11a8f7b/mathext/internal/amos/amoslib/myatan.f (about)

     1        DOUBLE PRECISION FUNCTION MYATAN(A)
     2        DOUBLE PRECISION A
     3        MYATAN = DATAN(A)
     4        RETURN
     5        END