concavity of curve

statistics statistical data background diagram distribution sigmoid artificial error function euler mathematics coordinate concave decrease concavity curve slopes differentiable plot convex concavity direction change decreasing inflection school grey blue colorful black college downward symbol sign simple second element upward concave shape slope graph parabola theorem tangent lines science interval mathematical minimum chart maximum increasing decreases positive draw teach inflection point learn figure graphic vector definition maxima negative minima convexity derivative icon second university maths line study poster math