对任意的锐角α、β,下列不等关系中正确的是( ) A.sin(α+β)>sinα+sinβ B.sin(α+β)>cosα+cosβ C.cos(α+β)<sinα+sinβ D.cos(α+β)<cosα+cosβ 答案:解析: 解法一:特殊值法:令α=β=30°,sin(α+β)=sin60°<sin30°+sin30°=1.所以A不对. sin(α+β)=sin60°<cos30°+cos30°=3. 所以B不对.cos(α+β)=cos60°<sin30°+sin30°,cos(α+β)=cos60°<cos30°+cos30°,C、D无法判断正确与否. 再令α=β=1°,则cos(α+β)=cos2°,sinα+sinβ=2sin1°. 因为cos2°>2When she heard the bad news, she couldn't help ________.A.cryB.to cryC.cryingD.cried