let u be Element of REAL 3; :: thesis: for f being PartFunc of (REAL 3),REAL st f is_hpartial_differentiable`13_in u holds
hpartdiff13 (f,u) = partdiff ((pdiff1 (f,1)),u,3)
let f be PartFunc of (REAL 3),REAL; :: thesis: ( f is_hpartial_differentiable`13_in u implies hpartdiff13 (f,u) = partdiff ((pdiff1 (f,1)),u,3) )
assume A1: f is_hpartial_differentiable`13_in u ; :: thesis: hpartdiff13 (f,u) = partdiff ((pdiff1 (f,1)),u,3)
consider x0, y0, z0 being Element of REAL such that
A2: u = <*x0,y0,z0*> by FINSEQ_2:103;
hpartdiff13 (f,u) = diff ((SVF1 (3,(pdiff1 (f,1)),u)),z0) by A1, A2, Th12
.= partdiff ((pdiff1 (f,1)),u,3) by A2, PDIFF_4:21 ;
hence hpartdiff13 (f,u) = partdiff ((pdiff1 (f,1)),u,3) ; :: thesis: verum