f(x)=cosx-(sinx)^2的最大值

f(x)=cosx-(sinx)^2的最大值

∵f(x)=cosx-1+cos²;x =cos²;x+cosx+1/4-5/4 =(cosx+1/2)²;-5/4又│cosx│≤1 ==>-1≤cosx≤1 ==>-1/2≤cosx+1/2≤3/2 ==>-3/2≤cosx+1/2≤3…