Source: 1990 National High School Mathematics League, Exam One, Problem 1
February 26, 2020
Problem Statement
Let α∈(4π,2π), then the order of (cosα)cosα,(sinα)cosα,(cosα)sinα is
(A)(cosα)cosα<(sinα)cosα<(cosα)sinα(B)(cosα)cosα<(cosα)sinα<(sinα)cosα(C)(sinα)cosα<(cosα)cosα<(cosα)sinα(D)(cosα)sinα<(cosα)cosα<(sinα)cosα