数学三角函数化简,求详细化简过程,谢谢

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数学三角函数化简,求详细化简过程,谢谢
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数学三角函数化简,求详细化简过程,谢谢
数学三角函数化简,求详细化简过程,谢谢

 

数学三角函数化简,求详细化简过程,谢谢

在△ABC中,cos2A-cos2B=2cos(π/6-A)cos(π/6+A),求∠B.
cos2A-cos2B=cos2A+cos(π/3)
故cos2B=-cos(π/3)=cos(π-π/3)=cos(2π/3)或cos2B=cos(π+π/3)=cos(4π/3)
∴2B=2π/3;B=π/3;或2B=4π/3,B=2π/3;