如图，⊙O是△ABC的外接圆，若⊙O的半径为2.5，AC=3，AC≠AB，则tanB的值为$\frac{3}{4}$．
17．在△ABC中，∠C=90°，若∠B=2∠A，则tanA等于（ ）
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| A． | $\sqrt{3}$ | B． | $\frac{{\sqrt{3}}}{3}$ | C． | $\frac{{\sqrt{3}}}{2}$ | D． | $\frac{1}{2}$ |
如图所示，直线AB、CD相交于O，OE平分∠AOC，若∠1=36°，则∠AOD=108°．