(* *)
(**************************************************************************)
-set "baseuri" "cic:/matita/demo/power_derivative".
-
include "nat/plus.ma".
include "nat/orders.ma".
include "nat/compare.ma".
elim n 0.
case O.
the thesis becomes (D[x \sup 0] = 0·x \sup (pred 0)).
- by _
done.
case S (m:nat).
by induction hypothesis we know
(D[x \sup (1+m)] = (1+m) · x \sup m).
we need to prove
(m · (x \sup (1+ pred m)) = m · x \sup m) (Ppred).
- by _ we proved (0 < m ∨ 0=m) (cases).
+ we proved (0 < m ∨ 0=m) (cases).
we proceed by induction on cases
to prove (m · (x \sup (1+ pred m)) = m · x \sup m).
case left.
suppose (0 < m) (m_pos).
- by (S_pred m m_pos) we proved (m = 1 + pred m) (H1).
- by _
+ using (S_pred ? m_pos) we proved (m = 1 + pred m) (H1).
done.
case right.
- suppose (0=m) (m_zero). by _ done.
+ suppose (0=m) (m_zero).
+ done.
conclude
(D[x \sup (1+m)])
- = (D[x · x \sup m]) by _.
- = (D[x] · x \sup m + x · D[x \sup m]) by _.
- = (x \sup m + x · (m · x \sup (pred m))) by _.
-clear H.
- = (x \sup m + m · (x \sup (1 + pred m))) by _.
- = (x \sup m + m · x \sup m) by _.
- = ((1+m) · x \sup m) by _ (timeout=30)
+ = (D[x · x \sup m]).
+ = (D[x] · x \sup m + x · D[x \sup m]).
+ = (x \sup m + x · (m · x \sup (pred m))) timeout=30.
+ = (x \sup m + m · (x \sup (1 + pred m))).
+ = (x \sup m + m · x \sup m).
+ = ((1+m) · x \sup m) timeout=30 by Fmult_one_f, Fmult_commutative, Fmult_Fplus_distr, costante_sum
done.
qed.
(D[x \sup (1+n)] = (1+n) · x \sup n).*) elim n 0.
case O.
the thesis becomes (D[x \sup 1] = 1 · x \sup 0).
- by _
done.
case S (m:nat).
by induction hypothesis we know
(D[x \sup (2+m)] = (2+m) · x \sup (1+m)).
conclude
(D[x \sup (2+m)])
- = (D[x · x \sup (1+m)]) by _.
- = (D[x] · x \sup (1+m) + x · D[x \sup (1+m)]) by _.
- = (x \sup (1+m) + x · (costante (1+m) · x \sup m)) by _.
-clear H.
- = (x \sup (1+m) + costante (1+m) · x \sup (1+m)) by _.
- = (x \sup (1+m) · (costante (2 + m))) by _
+ = (D[x · x \sup (1+m)]).
+ = (D[x] · x \sup (1+m) + x · D[x \sup (1+m)]).
+ = (x \sup (1+m) + x · (costante (1+m) · x \sup m)).
+ = (x \sup (1+m) + costante (1+m) · x \sup (1+m)).
+ = ((2+m) · x \sup (1+m)) timeout=30 by Fmult_one_f, Fmult_commutative,
+ Fmult_Fplus_distr, assoc_plus, plus_n_SO, costante_sum
done.
-qed.
\ No newline at end of file
+qed.