f(x)=sin2x+cos2x+1=√2sin(2x+π/4)+1f(C)=√2sin(2C+π/4)+1=2∴sin(2C+π/4)=√2/20＜C＜π,∴π/4＜2C+π/4＜2π+π/4∴2C+π/4=3π/4 ∴C=π/4由余弦定理知cosC=（a²+b²-c²)/2ab=√2/2∴(9-c
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