7-gon at 7.45E-15 (P22)

it took me a lot effort to reach this accuracy. I tried traditional way I used to be but failed. So I thought it might to have some new approch and this method is one . I just found that it is hard to use currecnt computer to find a good method at E-15 as the computer don't have enough lenth for the digits. I am happy to find this.