A. x=3cos(πt-π/2) B. x=3cos(πt+π/2) C. x=7cos(πt+π/2) D. x=7cos(πt-π/2)
A. x=13cos(πt-π/3) B. x=3cos(πt-π/3) C. x=3cos(πt-2π/3) D. x=13cos(πt-2π/3)