设cos (x +π/4 )＝3/5,17π/12
问题描述：
设cos (x +π/4 )＝3/5,17π/12
答
∵17π/12sinx+cosx=-4√2/5.(2)∴由(2)-(1)得2sinx=-7√2/5 ==>sinx=-7√2/10由(2)+(1)得2cosx=-√2/5 ==>cosx=-√2/10故(sin2x+2sin²x)/(1-tan x)=(2sinxcosx+2sin²x)/(1-sinx/cosx)=2sinx(cosx+sinx)/(...