f'(x)=1/2-cosx=0,且x∈[0,π]
=>cosx=1/2
=>x=π/3
又f(0)=0,f(π)=π/2 ,f(π/3)=π/6 -√3/2
=>则f(x)在区间（0,派）上最小值是f(π/3)=π/6 -√3/2