1 + cos(x-y) > 2 sin(x) sin(y), which is 1+cos(x+y) >0
• 三角公式啊 -trivial- ♀ (94 bytes) () 01/29/2012 postreply 17:55:46
• 绝,高手! -yasas- ♂ (0 bytes) () 01/29/2012 postreply 20:27:03