Finding the Constant of Integration (DP IB Analysis & Approaches (AA)): Revision Note

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Finding the Constant of Integration

What is the constant of integration? 

  • When finding an anti-derivative there is a constant term to consider

    • this constant term, usually called c, is the constant of integration

  • In terms of graphing an anti-derivative, there are endless possibilities

    • collectively these may be referred to as the family of antiderivatives or family of curves

    • the constant of integration is determined by the exact location of the curve

      • if a point on the curve is known, the constant of integration can be found

 

How do I find the constant of integration?

  • For straight F left parenthesis x right parenthesis plus c equals integral f left parenthesis x right parenthesis space straight d x, the constant of integration, c - and so the particular antiderivative - can be found if a point the graph of y equals straight F left parenthesis x right parenthesis plus c passes through is known 

 STEP 1

 If need be, rewritespace f left parenthesis x right parenthesis into an integrable form

 Each term needs to be a power of x (or a constant)

 

 STEP 2

 Integrate each term ofspace f apostrophe left parenthesis x right parenthesis, remembering the constant of integration, “plus c

 (Increase power by 1 and divide by new power)

 

 STEP 3

Substitute the x and y coordinates of a given point in to straight F left parenthesis x right parenthesis plus c to form an equation in c

Solve the equation to find c

Examiner Tips and Tricks

  • If a constant of integration can be found then the question will need to give you some extra information

    • If this is given then make sure you use it to find the value of c

Worked Example

The graph of y equals f left parenthesis x right parenthesis passes through the point left parenthesis 3 comma negative 4 right parenthesis.  The gradient function ofspace f left parenthesis x right parenthesis is given byspace f apostrophe left parenthesis x right parenthesis equals 3 x squared minus 4 x minus 4.

Findspace f left parenthesis x right parenthesis.

5-2-3-ib-sl-ai-aa-we1-soltn-

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Paul

Author: Paul

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Paul has taught mathematics for 20 years and has been an examiner for Edexcel for over a decade. GCSE, A level, pure, mechanics, statistics, discrete – if it’s in a Maths exam, Paul will know about it. Paul is a passionate fan of clear and colourful notes with fascinating diagrams.