:: deftheorem defines cD VSDIFF_1:def 7 :
for F, G being Field
for V being VectSp of F
for h being Element of V
for W being VectSp of G
for f being PartFunc of V,W holds cD (f,h) = (Shift (f,(((2 * (1. F)) ") * h))) - (Shift (f,(- (((2 * (1. F)) ") * h))));