Linear Approximation and Differential Examples

100 downloads 33011 Views 34KB Size Report
Linear approximation example: the table gives the population of Nepal (in ... Use a linear approximation to approximate the population in June of 1989. 1989 is ...
Linear approximation example: the table gives the population R Ð>Ñ of Nepal (in millions) in June of each year: > R Ð>Ñ

"*)& "(Þ!%

"**! "*Þ$$

"**& #"Þ*"

#!!! #%Þ(!

#!!& #(Þ')

Use a linear approximation to approximate the population in June of 1989.

1989 is close to 1990 (a time when we have some actual data), so we look at the linear approximation ( œ tangent line approximation) to the graph of R Ð>Ñ at + œ "**!Þ PÐ>Ñ

œ R Ð"**!Ñ  R w Ð"**!ÑÐ>  "**!Ñ œ "*Þ$$  R w Ð"**!ÑÐ>  "**!Ñ

We need to estimate R w Ð"**!Ñ À we do that, in the usual way, by averaging the slope of two secant lines:  "*Þ$$ "*Þ$$  "(Þ!% R w Ð"**!Ñ ¸ "# Ð #"Þ*" "**&  "**! Ñ  Ð "**!  "*)& ÑÑ ¸

¸ "# Ð!Þ&"'!  !Þ%&)!Ñ œ !Þ%)(! Ðmillions/year) So

PÐ>Ñ ¸ "*Þ$$  !Þ%)(! Ð>  "**!Ñ and we estimate PÐ"*)*Ñ ¸ "*Þ$$  !Þ%)(! Ð"*)*  "**!Ñ œ "*Þ$$  !Þ%)(! œ ")Þ)%$! ¸ ")Þ)% Ðmillions)

The graph below shows the population curve and also the tangent line approximation.

Example using differentials: The radius of a circular disk is given as 24 cm with a maximum error in measurement of 0.2 cm. Use differentials to estimate the maximum error in the calculated area of the disk. E œ 1