1. The problem statement, all variables and given/known data Prove for all real x and y that |sinx - siny| <= |x-y| 2. Relevant equations It's a question from the Mean Value Theorem/Rolle's Theorem section. 3. The attempt at a solution Honestly, I've tried. It looks somewhat similar to the triangle inequality (I think?), but truth be told I can't get anywhere with this. I'd appreciate if anyone could give me a hand and point me in the proper direction. Thanks!