(1) Cos15/8丌与cos14/9丌
Cos15/8丌=Cos1/8丌 cos14/9丌=cos4/9丌
∵0cos530°
3.sin(-54/7丌)与sin(-63/8丌)
sin(-54/7丌)=sin(2/7丌)
sin(-63/8丌)=sin(1/8丌)
且函数y=sinX在[0,1/2丌]上为增函数
sin(-54/7丌)>sin(-63/8丌)
(1) Cos15/8丌与cos14/9丌
Cos15/8丌=Cos1/8丌 cos14/9丌=cos4/9丌
∵0cos530°
3.sin(-54/7丌)与sin(-63/8丌)
sin(-54/7丌)=sin(2/7丌)
sin(-63/8丌)=sin(1/8丌)
且函数y=sinX在[0,1/2丌]上为增函数
sin(-54/7丌)>sin(-63/8丌)