Theorem itgeq1fOLD

Description: Obsolete version of itgeq1f as of 1-Sep-2025. (Contributed by Mario Carneiro, 28-Jun-2014) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Hypotheses	itgeq1f.1	$$⊢\underset{\_}{Ⅎ}xA$$
	itgeq1f.2	$$⊢\underset{\_}{Ⅎ}xB$$
Assertion	itgeq1fOLD	$$⊢A=B\to {\int }_{A}Cdx={\int }_{B}Cdx$$

Proof

Step	Hyp	Ref	Expression
1		itgeq1f.1	$$⊢\underset{\_}{Ⅎ}xA$$
2		itgeq1f.2	$$⊢\underset{\_}{Ⅎ}xB$$
3		eqid	$$⊢ℝ=ℝ$$
4	1 2	nfeq	$$⊢ℲxA=B$$
5		eleq2	$$⊢A=B\to \left(x\in A\leftrightarrow x\in B\right)$$
6	5	anbi1d	$$⊢A=B\to \left(\left(x\in A\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right)\leftrightarrow \left(x\in B\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right)\right)$$
7	6	ifbid	$$⊢A=B\to if\left(\left(x\in A\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)=if\left(\left(x\in B\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)$$
8	7	a1d	$$⊢A=B\to \left(x\in ℝ\to if\left(\left(x\in A\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)=if\left(\left(x\in B\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)\right)$$
9	4 8	ralrimi	$$⊢A=B\to \forall x\in ℝif\left(\left(x\in A\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)=if\left(\left(x\in B\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)$$
10		mpteq12	$$⊢\left(ℝ=ℝ\wedge \forall x\in ℝif\left(\left(x\in A\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)=if\left(\left(x\in B\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)\right)\to \left(x\in ℝ⟼if\left(\left(x\in A\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)\right)=\left(x\in ℝ⟼if\left(\left(x\in B\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)\right)$$
11	3 9 10	sylancr	$$⊢A=B\to \left(x\in ℝ⟼if\left(\left(x\in A\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)\right)=\left(x\in ℝ⟼if\left(\left(x\in B\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)\right)$$
12	11	fveq2d	$$⊢A=B\to {\int }^2\left(\left(x\in ℝ⟼if\left(\left(x\in A\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)\right)\right)={\int }^2\left(\left(x\in ℝ⟼if\left(\left(x\in B\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)\right)\right)$$
13	12	oveq2d	$$⊢A=B\to {\mathrm{i}}^k{\int }^2\left(\left(x\in ℝ⟼if\left(\left(x\in A\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)\right)\right)={\mathrm{i}}^k{\int }^2\left(\left(x\in ℝ⟼if\left(\left(x\in B\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)\right)\right)$$
14	13	sumeq2sdv	$$⊢A=B\to \sum _{k=0}^3{\mathrm{i}}^k{\int }^2\left(\left(x\in ℝ⟼if\left(\left(x\in A\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)\right)\right)=\sum _{k=0}^3{\mathrm{i}}^k{\int }^2\left(\left(x\in ℝ⟼if\left(\left(x\in B\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)\right)\right)$$
15		eqid	$$⊢\Re \left(\frac{C}{{\mathrm{i}}^k}\right)=\Re \left(\frac{C}{{\mathrm{i}}^k}\right)$$
16	15	dfitg	$$⊢{\int }_{A}Cdx=\sum _{k=0}^3{\mathrm{i}}^k{\int }^2\left(\left(x\in ℝ⟼if\left(\left(x\in A\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)\right)\right)$$
17	15	dfitg	$$⊢{\int }_{B}Cdx=\sum _{k=0}^3{\mathrm{i}}^k{\int }^2\left(\left(x\in ℝ⟼if\left(\left(x\in B\wedge 0\le \Re \left(\frac{C}{{\mathrm{i}}^k}\right)\right),\Re \left(\frac{C}{{\mathrm{i}}^k}\right),0\right)\right)\right)$$
18	14 16 17	3eqtr4g	$$⊢A=B\to {\int }_{A}Cdx={\int }_{B}Cdx$$