A:It is summer.
B:It is hot.
—The weather is very good. Let's have a picnic. — .
(1)用反证法证明:在一个三角形中,至少有一个内角大于或等于60°.
(2)已知n≥0,试用分析法证明:n+2-n+1<n+1-n.
跨经度最多的大洲是( )