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082-Engineering-Mathematics-Anthony-Croft-Robert-Davison-Martin-Hargreaves-James-Flint-Edisi-5-2017

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11 Techniquesof

differentiation

Contents 11.1 Introduction 386

11.2 Rulesofdifferentiation 386

11.3 Parametric,implicitandlogarithmicdifferentiation 393

11.4 Higherderivatives 400

Reviewexercises11 404

11.1 INTRODUCTION

InthischapterwedevelopthetechniquesofdifferentiationintroducedinChapter10so

thatratesofchangeofmorecomplicatedfunctionscanbefound.Weintroducerulesfor

differentiatingproductsandquotientsoffunctions.Thechainruleisusedfordifferentiating

functions of functions. We explain what is meant by defining functions implicitly

andparametricallyandshowhowthesecanbedifferentiated.Thetechniqueoflogarithmic

differentiation allows complicated products of functions to be simplified and then

differentiated.Finallyderivativesoffunctionscanthemselvesbedifferentiated.Thisinvolvestheuseofhigherderivativeswhichareexplainedtowardstheendofthechapter.

11.2 RULESOFDIFFERENTIATION

Therearethreeruleswhichenableustodifferentiatemorecomplicatedfunctions.They

are (a) the product rule, (b) the quotient rule, (c) the chain rule. Traditionally they are

written withxas the independent variable but apply in an analogous way for other independent

variables.

11.2.1 Theproductrule

Asthenamesuggests,thisruleallowsustodifferentiateaproductoffunctions,suchas

xsinx,t 2 cos2t and e z lnz.

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