如图,水坝的横截面是梯形ABCD,迎水坡BC的坡度i为1:√3,背水坡的坡角α为45°,坝顶宽CD和坝高均为6m求:1.迎水坡的坡角β2.坝底宽AB的长(精确到0.1m,√2≈1.414,√3≈1.732)