50KiB, 971x550, 4536-nearly-otc15c2.png View SameGoogleiqdbSauceNAO Anonymous Fri 12 Feb 01:53:56 2021 No.12695782 ViewReplyOriginalReport Quoted By: >>12695784 >>12696082 >>12698745 ?? f(x,y) dxdy ? ?? f(x,y) dxdy ^^^^ Why can't I find the theory behind when this is true?