单项选择题
A.(√0.5)kcos(0.25kπ-0.25π)B.√2(√0.5)kcos(0.25kπ-0.25π)C.√2(√0.5)kcos(0.5kπ-0.5π)D.2(√0.5)kcos(0.25kπ-0.5π)
A.AB.BC.CD.D
A.0<k<26.5B.1.35<k<3.68C.0.36<k<4.21D.1.35<k<4.21