The rate of change of moment coefficient with respect to the angle of attack, $\frac{\mathrm{d} \mathrm{C}_{\mathrm{m}}}{\mathrm{d} \alpha},$ at half chord point of a thin airfoil, as per approximations from the thin airfoil theory is
(A) $\pi / 4$ radian $^{-1}$
(B) $\pi / 2$ radian $^{-1}$
(C) $\pi$ radian $^{-1}$
(D) $2 \pi$ radian $^{-1}$
The rate of change of moment coefficient with respect to the angle of attack, $\frac{\mathrm{d} \mathrm{C}_{\mathrm{m}}}{\mathrm{d} \alpha},$ at half chord point of a thin airfoil, as per approximations from the thin airfoil theory is
(A) $\pi / 4$ radian $^{-1}$
(B) $\pi / 2$ radian $^{-1}$
(C) $\pi$ radian $^{-1}$
(D) $2 \pi$ radian $^{-1}$