The minimum value of function y = (SiN x) ^ 4 + (COS x) ^ 2, X ∈ [0,6 / π] is -——

The minimum value of function y = (SiN x) ^ 4 + (COS x) ^ 2, X ∈ [0,6 / π] is -——

Please note: B of a should be written as B / A, y = (SiNx) ^ 4 + (cosx) &# 178; = (Sin & # 178; x) &# 178; + 1-sin & # 178; X let t = Sin & # 178; X, X ∈ [0, π / 6], then t ∈ [0,1 / 4] y = T & # 178; - t + 1 this quadratic function has an opening upward, and the axis of symmetry is t = 1 / 2, so it is monotonically decreasing in [0,1 / 4], so when t =