拜托了，数学题 50
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1)f(x)=mn= √3sinx/3*cosx/3+(cosx/3)^2
=√3/2*sin2x/3+1/2(1+cos2x/30
=(√3/2*sin2x/3+1/2cos2x/3)+1/2
=sin(2x/3+π/6)+1/2
T=2π/(2/3)=3π
2kπ-π/2≤2x/3+π/6≤2kπ+π/2
2kπ-2π/3≤2x/3≤2kπ+π/3
3kπ-π≤x≤3kπ+π/2
单调递增为:[3kπ-π ,3kπ+π/2]
2) (2a-b)cosC=c cosB
(2sinA-sinB)cosC=sinCcosB
2sinAcosC=sinBcosC+sinCcosB
2sinAcosC=sin(B+C)
2sinAcosC=sinA
cosC=1/2
C=π/3
=√3/2*sin2x/3+1/2(1+cos2x/30
=(√3/2*sin2x/3+1/2cos2x/3)+1/2
=sin(2x/3+π/6)+1/2
T=2π/(2/3)=3π
2kπ-π/2≤2x/3+π/6≤2kπ+π/2
2kπ-2π/3≤2x/3≤2kπ+π/3
3kπ-π≤x≤3kπ+π/2
单调递增为:[3kπ-π ,3kπ+π/2]
2) (2a-b)cosC=c cosB
(2sinA-sinB)cosC=sinCcosB
2sinAcosC=sinBcosC+sinCcosB
2sinAcosC=sin(B+C)
2sinAcosC=sinA
cosC=1/2
C=π/3
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