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Derivatives

Derivatives

Tangent Line Approximation

There are only two things we need to remember about the tangent line to f at a.

  • The tangent line and f have the same y-value at a.  
      
    That is, the point (a, f(a)) is on f and also on the tangent line to f at a.

  • The tangent line and f have the same slope at a.  
      
    That is, the slope of the tangent line to f at a is f'(a).

That's it. If we can we remember those two things we'll be good when it comes to tangent lines.

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