b
\(y=\sin \omega t+\cos \omega t\)

\(y=\sin \omega t+\sin \left(\omega t+\frac{\pi}{2}\right)\)

\(\Delta \phi=\frac{\pi}{2}\)

\(A _{\text {net }}=\sqrt{1^2+1^2+2 \times 1 \times 1 \times \cos (\Delta \phi)}\)

\(A _{\text {met }}=\sqrt{2}\)