若tan=1/2 x属于(0,1/4π) 则sin(2x+1/4π)=
问题描述:
若tan=1/2 x属于(0,1/4π) 则sin(2x+1/4π)=
答
sin(2x+1/4π)=1/根号2(sin2x+cos2x)=1/根号2(2sinxcosx+cos^2-sin^2)=【1/根号2(2sinxcosx+cos^2-sin^2)】/(sin^2x+cos^2)分子分母同除cos^2得(2tanx-tan^2+1)/根号2(tan^2+1)又tan=1/2 所以=7根号2/1...我算的咋是十分之九倍根号二你分子符号有错
2tanx-tan^2+1
如果搞成2tanx+tan^2+1,那就跟我不一样了好吧 谢谢