MathDB
Order the Numbers

Source: 1990 National High School Mathematics League, Exam One, Problem 1

February 26, 2020

Problem Statement

Let α(π4,π2)\alpha\in(\frac{\pi}{4},\frac{\pi}{2}), then the order of (cosα)cosα,(sinα)cosα,(cosα)sinα(\cos\alpha)^{\cos\alpha},(\sin\alpha)^{\cos\alpha},(\cos\alpha)^{\sin\alpha} is (A)(cosα)cosα<(sinα)cosα<(cosα)sinα\text{(A)}(\cos\alpha)^{\cos\alpha}<(\sin\alpha)^{\cos\alpha}<(\cos\alpha)^{\sin\alpha} (B)(cosα)cosα<(cosα)sinα<(sinα)cosα\text{(B)}(\cos\alpha)^{\cos\alpha}<(\cos\alpha)^{\sin\alpha}<(\sin\alpha)^{\cos\alpha} (C)(sinα)cosα<(cosα)cosα<(cosα)sinα\text{(C)}(\sin\alpha)^{\cos\alpha}<(\cos\alpha)^{\cos\alpha}<(\cos\alpha)^{\sin\alpha} (D)(cosα)sinα<(cosα)cosα<(sinα)cosα\text{(D)}(\cos\alpha)^{\sin\alpha}<(\cos\alpha)^{\cos\alpha}<(\sin\alpha)^{\cos\alpha}