The following equalities are obvious, but they are beautiful nonetheless.
1 × 1 = 1
11 × 11 = 121
111 × 111 = 12321
1111 × 1111 = 1234321
11111 × 11111 = 123454321
111111 × 111111 = 12345654321
1111111 × 1111111 = 1234567654321
11111111 × 11111111 = 123456787654321
111111111 × 111111111 = 12345678987654321
1 × 9 + 2 = 11
12 × 9 + 3 = 111
123 × 9 + 4 = 1111
1234 × 9 + 5 = 11111
12345 × 9 + 6 = 111111
123456 × 9 + 7 = 1111111
1234567 × 9 + 8 = 11111111
12345678 × 9 + 9 = 111111111
12 - 1 = 11
123 - 12 = 111
1234 - 123 = 1111
12345 - 1234 = 11111
123456 - 12345 = 111111
1234567 - 123456 = 1111111
12345678 - 1234567 = 11111111
123456789 - 12345678 = 111111111
I hope you enjoyed these beautiful equations. Another type of beautiful formulas are continuous fractions and infinite sum series that I hope to post about them later.