若3π/2<α<2π,化简√{(1/2)+(1/2)√[(1/2)+(1/2)cos2α]}求大神帮助用讨论吗 是从“二倍角的正弦 余弦 正切”

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若3π/2<α<2π,化简√{(1/2)+(1/2)√[(1/2)+(1/2)cos2α]}求大神帮助用讨论吗是从“二倍角的正弦余弦正切”若3π/2<α<2π,化简√{(1/2)+(1/2)√[(1/

若3π/2<α<2π,化简√{(1/2)+(1/2)√[(1/2)+(1/2)cos2α]}求大神帮助用讨论吗 是从“二倍角的正弦 余弦 正切”
若3π/2<α<2π,化简√{(1/2)+(1/2)√[(1/2)+(1/2)cos2α]}求大神帮助
用讨论吗 是从“二倍角的正弦 余弦 正切”

若3π/2<α<2π,化简√{(1/2)+(1/2)√[(1/2)+(1/2)cos2α]}求大神帮助用讨论吗 是从“二倍角的正弦 余弦 正切”
√{(1/2)+(1/2)√[(1/2)+(1/2)cos2α]} (cos2α = 2(cosα) -1) =√{(0.5+0.5√(0.5+0.5[2(cosα) -1])} =√{[0.5+0.5√(cosα)]} (因為3π/2<α<2π,α在第四象限,所以cosα > 0) =√{[0.5+0.5cosα]} (cosα = 2(cos(α/2)) -1) =√{(0.5+0.5[(2cos(α/2) -1])} =√(cos(α/2)) (因为3π/2<α<2π,所以3π/4<α/2<π,α/2在第二象限 所以cos(α/2) < 0) = -cos(α/2)

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