若tanα=（√15）,则cosα=?sinα=?
问题描述：
若tanα=（√15）,则cosα=?sinα=?
答
(secα)^2 = 1 + (tanα)^2 = 1 + 15 =16
secα=±4
cosα=1/secα=±1/4
sinα=±√[1-(cosα)^2]=±√15/4