y=2cosxsinx+2cos^2x=sin2x+cos2x+1=根号2sin（2x+π/4）+1
sina的递增区间为2kπ-π/2大于a小于2kπ+π/2 2x+π/4=a算出x的取值
sina的对称中心为kπ 2x+π/4=kπ算出x
sina的对称轴为kπ+π/2 2x+π/4=kπ+π/2算出x