Question

cos(π/3 + A) = sin(π/6 - A)

Answer 1

$\cos(\frac{\pi}{3} + A) = \cos\frac{\pi}{3} \cos A - \sin \frac{\pi}{3} \sin A = \sin\frac{\pi}{6} \cos A - \cos \frac{\pi}{6} \sin A = \sin (\frac{\pi}{6} - A)$ as desired.