若集合A={α|180K+30<α<180K +90,K∈Z},集合B={β|360k+315<β<360k+405,k∈Z},求A∩B

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若集合A={α|180K+30<α<180K +90,K∈Z},集合B={β|360k+315<β<360k+405,k∈Z},求A∩B
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若集合A={α|180K+30<α<180K +90,K∈Z},集合B={β|360k+315<β<360k+405,k∈Z},求A∩B
若集合A={α|180K+30<α<180K +90,K∈Z},集合B={β|360k+315<β<360k+405,k∈Z},求A∩B

若集合A={α|180K+30<α<180K +90,K∈Z},集合B={β|360k+315<β<360k+405,k∈Z},求A∩B
α ,180K+30<α<180K +90等价于360k+30<α<360k+90,
且180(2K+1)+30<α<180(2K+1)+90,即360k+210<α<360k+270
故A={α|360k+30<α<360k+90且360k+210<α<360k+270k∈Z}.
β ,360k+315<β<360k+405,即360k+315<β<360k+360
且360k<β<360k+45
故B={β|360k<β<360k+45且360k+315<β<360k+360k∈Z},
A∩B={θ|360k+30<θ<360k+45,k∈Z}.

这是关于象限的问题。A集合可以分为两个集合{α|360K+30<α<360K +90,K∈Z}与{α|360K+210<α<360K +270,K∈Z},B集合可写成{β|360k-45<β<360k+45,k∈Z},画图就可知A∩B=={β|360k+30<β<360k+45,k∈Z}

数学必修4
α ,180K+30<α<180K +90等价于360k+30<α<360k+90,
且180(2K+1)+30<α<180(2K+1)+90,即360k+210<α<360k+270
故A={α|360k+30<α<360k+90且360k+210<α<360k+270k∈Z}。
β , 360k+315<β<360k+405,即360...

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数学必修4
α ,180K+30<α<180K +90等价于360k+30<α<360k+90,
且180(2K+1)+30<α<180(2K+1)+90,即360k+210<α<360k+270
故A={α|360k+30<α<360k+90且360k+210<α<360k+270k∈Z}。
β , 360k+315<β<360k+405,即360k+315<β<360k+360
且360k<β<360k+45
故B={β|360k<β<360k+45且360k+315<β<360k+360k∈Z},
A∩B={θ|360k+30<θ<360k+45,k∈Z}。

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