Which of these four numbers is the smallest?

cos1° ≈ 0.9998 and cot1° ≈ 57.29 are far larger than the other two, so the contest is between sin1° and tan1°. For any acute angle tanθ = sinθ/cosθ with 0 < cosθ < 1, so tanθ > sinθ: here sin1° ≈ 0.0174524 against tan1° ≈ 0.0174551. The smallest is sin1°.