f(x)=1-(cosx)平方,x属于[-π/4,π/4],其单调递增区间为____
问题描述：
f(x)=1-(cosx)平方,x属于[-π/4,π/4],其单调递增区间为____
答
f(x)=1-cos²x=sin²x=1/2(1-cos2x)
∵单调递增
∴cos2x单调递减
∵x属于[-π/4,π/4],
∴2x∈[-π/2,π/2]
∴2x∈[0,π/2]
∴x∈[0,π/4]