1, first replace sin^2x with 1-cos 2x.

2,Y=cos^2x-2cosx+2

3. According to 30 ≤ x ≤ 60, the range of cosine in this range is 1/2- and 3/2.

4, let cosx=T, so y = t 2-2t+2 (1/2

5. Find the maximum value of the quadratic function in a given interval and use the mirror image method to get it.

Do it yourself so that you can use it flexibly next time!