1-(sin²a+cos²a)(sin²a+sinacosa+cos²a)][1-(sin²a+cos²a)-3sin²acos²a]这怎么变得 怎么从上变到下的
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![1-(sin²a+cos²a)(sin²a+sinacosa+cos²a)][1-(sin²a+cos²a)-3sin²acos²a]这怎么变得 怎么从上变到下的](/uploads/image/z/8914388-68-8.jpg?t=1-%28sin%26%23178%3Ba%2Bcos%26%23178%3Ba%29%28sin%26%23178%3Ba%2Bsinacosa%2Bcos%26%23178%3Ba%29%5D%5B1-%28sin%26%23178%3Ba%2Bcos%26%23178%3Ba%29-3sin%26%23178%3Bacos%26%23178%3Ba%5D%E8%BF%99%E6%80%8E%E4%B9%88%E5%8F%98%E5%BE%97++%E6%80%8E%E4%B9%88%E4%BB%8E%E4%B8%8A%E5%8F%98%E5%88%B0%E4%B8%8B%E7%9A%84)
1-(sin²a+cos²a)(sin²a+sinacosa+cos²a)][1-(sin²a+cos²a)-3sin²acos²a]这怎么变得 怎么从上变到下的
1-(sin²a+cos²a)(sin²a+sinacosa+cos²a)]
[1-(sin²a+cos²a)-3sin²acos²a]这怎么变得 怎么从上变到下的
1-(sin²a+cos²a)(sin²a+sinacosa+cos²a)][1-(sin²a+cos²a)-3sin²acos²a]这怎么变得 怎么从上变到下的
1-(sin²a+cos²a)(sin²a+sinacosa+cos²a)]
=1-(sin²a+sinacosa+cos²a)
=1-(1+sinacosa)
=-1/2sin2a
郭敦顒回答:
∵sin²a+cos²a=1
∴1-(sin²a+cos²a)(sin²a+sinacosa+cos²a)]
=1-(1+ sinacosa)
= sinacosa=(1/2)(sin2a +1 )
三角函数的积化和差公式:
sinαcosβ=(1/2)[sin(α+β)+co...
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郭敦顒回答:
∵sin²a+cos²a=1
∴1-(sin²a+cos²a)(sin²a+sinacosa+cos²a)]
=1-(1+ sinacosa)
= sinacosa=(1/2)(sin2a +1 )
三角函数的积化和差公式:
sinαcosβ=(1/2)[sin(α+β)+cos(α-β)] , cos(a-a)=1,
[1-(sin²a+cos²a) -3sin²acos²a]=1-1-3(sinacosa)²
=-(3/4)(sin 2a+1)²,
∴1-(sin²a+cos²a)(sin²a+sinacosa+cos²a)] ≠[1-(sin²a+cos²a) -3sin²acos²a]。
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