sin2a/ cos^2 a =2sinacos a / cos^2 a =2tana=2*3=6sin^2 a+cos2a=sin^2 a+cos^2a-sin^2 a =1/4 cos^2a =1/4 cosa =1/2tana=√3F(x)=3sin^2 πx/2 +1=3/2[1-cosπx]+1 最小正周期为2C的值为2f(x)=(1+根号2cos(2x-π/4)) / sin(x+π/2)求定义域会吗？谢谢2cos(2x-π/4)≥0 2kπ-π/2≤2x-π/4≤2kπ+π/2kπ-π/2≤x≤kπ+3π/2sin(x+π/2)≠0x+π/2 ≠kπx≠kπ -π/2交集即可kπ-π/2＜x＜kπ+π/2