已知函数y=2sin(x+π2)cos(x−π2)与直线y=12相交,若在y轴右侧的交点自左向右依次记为M1,M2,M3,…,则|M1M13|等于(  ) A.6π B.7π C.12π D.13π

问题描述:

已知函数y=2sin(x+

π
2
)cos(x−
π
2
)与直线y=
1
2
相交,若在y轴右侧的交点自左向右依次记为M1,M2,M3,…,则|
M1M13
|
等于(  )
A. 6π
B. 7π
C. 12π
D. 13π

∵y=2sin(x+π2)cos(x-π2)=2cosxsinx=sin2x,∴由题意得:sin2x=12,∴2x=2kπ+π6或2x=2kπ+5π6,∴x=kπ+π12或x=kπ+5π12,k∈Z,∵正弦曲线y=sin2x与直线y=12在y轴右侧的交点自左向右依次记为M1,M2,M3...