What is the minimum value of 3 (A+(π)/(3)) where A ∈ R ?

Let y=3 \cdot \cos \left( A+\frac{\pi}{3}\right), y^{\prime}=-3 \cdot \sin \left( A+\frac{\pi}{3}\right) For extremum value, y^{\ prime}=0\begin{\text{ aligned }} & \sin \left( A+\frac{\pi}{3}\right)=0 \Rightarrow A+\frac{\pi}{3}=0 \Rightarrow A=-\frac{\pi}{3}\\ & y^{\prime \prime}=-3\cdot \cos \left(A+\frac{\pi}{3}\right)\\ & \quad=-3 \cos \left(-\frac{\pi}{3}+\frac{\pi}{3}\right)=-3 \cos (0)=-3 \end{aligned}