Differentiate algebraic and trigonometric equations, rate of change, stationary points, nature, curve sketching, and equation of tangent in Higher Maths.

Wim Vervaat, On a Stochastic Difference Equation and a Representation of Non-Negative Infinitely Divisible Random Variables, Advances in Applied Probability, Vol. 11, No. 4 (Dec., 1979), pp. 750-783 ...