已知α、β∈(0,π/2),且cosα>sinβ,则α+β与π/2的大小关系:A.α+β>π/2 b..α+β<π/2 Cα+β≥π/2 D.α+β≤π/2方程cos(5π/2+x)=(1/2)^X在区间(0,100π)内解的个数是