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11. ½â:h(x)?cos2(x??3)?1??2?sin(x?3)cos(x?3)?2

1?cos(2x?2 =

3?)2?12sin(2x?23?)?32 =

12cos(2x?23?)?12sin(2x?23?)?2 =

22[22cos(2x?23?)?222sin(2x?3?)]?2 =

2112cos(2x?12?)?2 ?h(x)max?2?22.

Õâʱ2x?1112??2k?,x?k??1124?.k?Z.

12.Èçͼ3,¼ÇÉÈOABµÄÖÐÐĽÇΪ45?,°ë¾¶Îª1,¾ØÐÎPQMNÄÚ½ÓÓÚÕâ¸öÉÈÐÎ,Çó¾ØÐεĶԽÇÏßlµÄ×îСֵ.

½â:Á¬½áOM,Éè¡ÏAOM=?.ÔòMQ=sin?,OQ=cos?,OP=PN=sin?. PQ=OQ-OP=cos??sin?.

B

l2?MQ2?PQ2

N

M

=sin2??(cos??sin?)2

=

32?(sin2??12cos2?) ?

=3?5sin(2?O

,ÆäÖÐ

P

Q

A

22??1)ͼ3

t?a1?11?n2,?1?(0,2),?1?arctan2.

ÊÔ¾íµÚ6Ò³£¬×Ü4Ò³

¡­Ïß¡­¡­¡­¡­¡ð¡­¡­¡­¡­

1?10???,?arctan?2???1??arctan.

4222??l2min355?1??,lmin?. 222ËùÒÔµ±???5?111. ?arctanʱ, ¾ØÐεĶԽÇÏßlµÄ×îСֵΪ

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