The equation should be
− 1 1 + 4 ( 0.5 ) π A = − 0.3 ⟹ A ≈ 0.27 , {\displaystyle -{\frac {1}{1+{\frac {4(0.5)}{\pi A}}}}=-0.3\qquad \Longrightarrow \qquad A\approx 0.27,}
Return to errata.
