一平面余弦波在t=0時(shí)刻的波形曲線如圖所示,則O點(diǎn)的振動(dòng)初相φ為:()
A.0 B.π/2 C.π D.3π/2或(-π/2)
A.x=2cos(50πt+0.25π) B.x=5cos(50πt) C. D.x=7
A.T/4; B.T/12; C.T/6; D.T/8。