Since sin(x) is concave on [0,π], we have sin(x)≥sin(0)+(x−0)sin(π/2)−sin(0)π/2−0=2xπ≥x2. enter image description here. ... <看更多>

答案是2xcos(x^2),我想問為什麼不是cos(x^2)?因為假使我令a=X^2，題目就變成d(sin(a)/dx，那sin的微分不就是cos?所以會成為cos(a)，那代回去不就又 ... ... <看更多>