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14. Tangent Lines and Rate of Change

Dated: 30-10-2024

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The secent line is the one which connects \(\overline{PQ}\).
The \(m_{sec}\) is the slope1
As the \(x_1 - x_0 \to 0\)

  • The secent line approaches the tangentline if \(x_1\) moves from right to \(x_0\).
  • The tangent line approaches the secentline if \(x_0\) moves from left to \(x_1\).

Therefore, the slope1 of tangent line is given by

\[m_{tan} = \lim_{x_1 \rightarrow x_0} \frac{f(x_1) - f(x_0)}{x_1 - x_0}\]

Average Velocity

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The distance is defined to be a function2 of time.
Since we are taking the snapshots from a very large gap in time, we say this is average not instantaneous rate of change.

\[Average = \frac{f(t_1) - f(t_0)}{t_1 - t_0}\]

Instantaneous Velocity

\[instantaneous =\lim_{t_1 \rightarrow t_0} \frac{f(t_1) - f(t_0)}{t_1 - t_0}\]

References

Read more about notations and symbols.


  1. Read more about slopes

  2. Read more about functions