已知函数f(x)=√3/2sin2x-cosx∧2-1/2,x∈R.急
2个回答

(1)f(x)=√3/2sin2x-cosx∧2-1/2

=√3/2sin2x-1/2*(cos2x+1)-1/2

=√3/2sin2x-1/2*cos2x-1

=sin(2x-π/6)-1

x∈R,所以2x-π/6∈R

所以最小值为-2,最小正周期T=π

(2)f(c)=0

sin(2c-π/6)=1

2c-π/6=π/2

c=π/3

根据余弦定理:c²=a²+b²-2abcosc

所以 √3 ²=a²+4a²-4a²cosπ/3

解得a=1,则b=2