???k???4,k?Z
2.解：2(2cos2B?1)?8cosB?5?0,4cos2B?8cosB?5?0
??a?b3413 得cosB?,sinB?，cos??????,sin??,
5522a?b sinB(???)3.解：?(4?33 sBin?c?osBco?s?sin10?????5?x)?(?x)?,?cos(?x)?sin(?x)?， 4424413???120?2x)?sin2(?x)?2sin(?x)cos(?x)? 2444169120cos2x12 ??169?。
?513cos(?x)413 而cos2x?sin(4.解：f(x)??13a3asin2x?(1?cos2x)?a?b 222a3asinx2?22coxs?2b?asxi?n(2?b )3 ?? （1）2k???235?11?,k??],k?Z为所求 ?[k??1212 （2）0?x??2x???2k??3?5?11?,k???x?k?? 21212?2,??3?2x??3?2?3?,??sin(2x?)?1 323 f(x)min??3a?b??2,f(xm)ax?a?b? 3,2?3?a?2a?b??2????? ?2 ??b??2?3?a?b?3?
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