let a, b be non zero Nat; :: thesis: ( a,b are_coprime implies ppf (a * b) = (ppf a) + (ppf b) )
assume A1: a,b are_coprime ; :: thesis: ppf (a * b) = (ppf a) + (ppf b)
reconsider an = a, bn = b as non zero Nat ;

now :: thesis: for i being object st i in SetPrimes holds
(ppf (a * b)) . i = ((ppf a) + (ppf b)) . i

A2: a gcd b = 1 by A1;
let i be object ; :: thesis: ( i in SetPrimes implies (ppf (a * b)) . b₁ = ((ppf a) + (ppf b)) . b₁ )
assume i in SetPrimes ; :: thesis: (ppf (a * b)) . b₁ = ((ppf a) + (ppf b)) . b₁
then reconsider p = i as prime Element of NAT by NEWTON:def 6;
A3: p > 1 by INT_2:def 4;
A4: p |-count (an * bn) = (p |-count a) + (p |-count b) by Th28;

per cases ( p |-count (a * b) = 0 or p |-count (a * b) <> 0 ) ;

suppose A5: p |-count (a * b) = 0 ; :: thesis: (ppf (a * b)) . b₁ = ((ppf a) + (ppf b)) . b₁

then A6: p |-count b = 0 by A4;
A7: p |-count a = 0 by A4, A5;
thus (ppf (a * b)) . i = 0 by A5, Th55
.= 0 + ((ppf b) . i) by A6, Th55
.= ((ppf a) . i) + ((ppf b) . i) by A7, Th55
.= ((ppf a) + (ppf b)) . i by PRE_POLY:def 5 ; :: thesis: verum

end;

suppose A8: p |-count (a * b) <> 0 ; :: thesis: (ppf (a * b)) . b₁ = ((ppf a) + (ppf b)) . b₁

thus (ppf (a * b)) . i = ((ppf a) + (ppf b)) . i :: thesis: verum

proof

per cases ( p |-count a <> 0 or p |-count b <> 0 ) by A4, A8;

suppose A9: p |-count a <> 0 ; :: thesis: (ppf (a * b)) . i = ((ppf a) + (ppf b)) . i

A10: now :: thesis: not p |-count b <> 0

consider ka being Nat such that
A11: p |-count a = ka + 1 by A9, NAT_1:6;
p |^ (p |-count a) divides a by A3, Def7;
then p * (p |^ ka) divides a by A11, NEWTON:6;
then consider la being Nat such that
A12: a = (p * (p |^ ka)) * la ;
a = p * ((p |^ ka) * la) by A12;
then A13: p divides a ;
assume p |-count b <> 0 ; :: thesis: contradiction
then consider kb being Nat such that
A14: p |-count b = kb + 1 by NAT_1:6;
p |^ (p |-count b) divides b by A3, Def7;
then p * (p |^ kb) divides b by A14, NEWTON:6;
then consider lb being Nat such that
A15: b = (p * (p |^ kb)) * lb ;
b = p * ((p |^ kb) * lb) by A15;
then p divides b ;
then p divides 1 by A2, A13, NAT_D:def 5;
hence contradiction by A3, NAT_D:7; :: thesis: verum

end;

hence (ppf (a * b)) . i = p |^ (p |-count a) by A4, A8, Th56
.= ((ppf a) . p) + 0 by A9, Th56
.= ((ppf a) . p) + ((ppf b) . p) by A10, Th55
.= ((ppf a) + (ppf b)) . i by PRE_POLY:def 5 ;
:: thesis: verum

end;

suppose A16: p |-count b <> 0 ; :: thesis: (ppf (a * b)) . i = ((ppf a) + (ppf b)) . i

A17: now :: thesis: not p |-count a <> 0

assume p |-count a <> 0 ; :: thesis: contradiction
then consider ka being Nat such that
A18: p |-count a = ka + 1 by NAT_1:6;
p |^ (p |-count a) divides a by A3, Def7;
then p * (p |^ ka) divides a by A18, NEWTON:6;
then consider la being Nat such that
A19: a = (p * (p |^ ka)) * la ;
a = p * ((p |^ ka) * la) by A19;
then A20: p divides a ;
consider kb being Nat such that
A21: p |-count b = kb + 1 by A16, NAT_1:6;
p |^ (p |-count b) divides b by A3, Def7;
then p * (p |^ kb) divides b by A21, NEWTON:6;
then consider lb being Nat such that
A22: b = (p * (p |^ kb)) * lb ;
b = p * ((p |^ kb) * lb) by A22;
then p divides b ;
then p divides 1 by A2, A20, NAT_D:def 5;
hence contradiction by A3, NAT_D:7; :: thesis: verum

end;

hence (ppf (a * b)) . i = p |^ (p |-count b) by A4, A8, Th56
.= 0 + ((ppf b) . p) by A16, Th56
.= ((ppf a) . p) + ((ppf b) . p) by A17, Th55
.= ((ppf a) + (ppf b)) . i by PRE_POLY:def 5 ;
:: thesis: verum

end;

end;

end;

end;

end;

end;

hence ppf (a * b) = (ppf a) + (ppf b) ; :: thesis: verum