已知cosx=-根号3/3,且18O度
问题描述：
已知cosx=-根号3/3,且18O度
答
cosx =-√3/3
sinx =-√6/3
tanx = sinx/cosx =√2
sin2x= 2sinxcosx =2√2/3
cos2x = (cosx)^2- (sinx)^2 = -1/9
tan2x= 2tanx/(1-(tanx)^2) = 2√2/ (1-2) =-2√2