1。 According to the conditions, [α-β] and α are both between 0 and dichotomy, so sin[α-β] is positive, that is, 3 root numbers 3/ 14, and sinα is positive, that is, 4 root numbers 3/7, so tanα is 4 root numbers 3 and tan2α is 2 tan α/ 1-tan α 2.

2。 cosβ= cos[α-(α-β)]= cosαcos(α-β)+sinαsin[α-β]= 1/2。

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