Where did that example come from? Why did they say the biasing resistors should equal R1?
The ratios are about RF and Rin and set the gain of the non-inverting op amp. Your circuit and the example circuits have different gain so the "=1/2 R1" does not apply.
The ratios are about RF and Rin and set the gain of the non-inverting op amp. Your circuit and the example circuits have different gain so the "=1/2 R1" does not apply.