填空题,①cosπ/5×cos2π/5=_______②函数y=1/1+sinΧ的定义域是_____③sin(α+30°)－sin(α-30°)/cosα=_____只给1，2两题的答案也得啊…

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填空题,①cosπ/5×cos2π/5=_______②函数y=1/1+sinΧ的定义域是_____③sin(α+30°)－sin(α-30°)/cosα=_____只给1，2两题的答案也得啊…填空题

填空题,①cosπ/5×cos2π/5=_______②函数y=1/1+sinΧ的定义域是_____③sin(α+30°)－sin(α-30°)/cosα=_____只给1，2两题的答案也得啊…
填空题,
①cosπ/5×cos2π/5=_______
②函数y=1/1+sinΧ的定义域是_____
③sin(α+30°)－sin(α-30°)/cosα=_____
只给1，2两题的答案也得啊…

填空题,①cosπ/5×cos2π/5=_______②函数y=1/1+sinΧ的定义域是_____③sin(α+30°)－sin(α-30°)/cosα=_____只给1，2两题的答案也得啊…
第一题你写的我看不懂,抱歉无法给你回答；
2.定义域是X不等于（二分之三排加上2k排）.
3.

1.0.25
2 x≠2/3+2kπ
3 √3/（2cosa）

cosπ/5×cos2π/5= cosπ/5cos2π/5=? 求COSπ/5*COS2π/5 COSπ/5乘以COS2π/5 cosπ/5×cos2π/5 cosπ/5cos2π/5 若cos(π-θ)=3/5,cos2θ= cos(π-θ)=3/5 求cos2θ cos(π- θcos2θ)=3/5 求 cosπ/5 - cos2π/5 怎样变成 cosπ/5 + cos2π/5rt （cosπ/5）（cos2π/5)的值等于 cosπ/5·cos2π/5等于多少? cosπ/5*cos2π/5的值等于 cosπ/5 乘以cos2π/5等于多少 化简cosπ/5cos2π/5RT. cosπ/5*cos2π/5 =(2sinπ/5*cosπ/5*cos2π/5)/(2sinπ/5) =(sin2π/5*cos2π/5)/(2sinπ/5) =(2sin2π/低2部咋算的? cosπ/5 +cos2π/5 +cos3π/5 +cos4π/5 =可以简写. 设sin(π/4+α)+cos(π/4+α)=-1/5,则cos2α=