Mathematics 150 AL

Notes for Assignment 2

Definition: A function $\ f$ defined on ($a,b$) is differentiable at a point $x$ in ($a,b$) if

MATH exists.

This limit is denoted by $\ f\prime (x)$.

MATH is called the difference quotient of $f$:

Example:

Let MATH

Define f using the definition option. Then use the evaluate option to determine MATH

MATH

go to "compute", then "expand"

MATH

and evaluate the limit as $h\rightarrow 0;$

MATH

MATH

Tangent lines: If the derivative of a function $f$ exists at a point $a$, then it

is equal to the slope of the tangent line of this function. Moreover, the equation

of the tangent line at this point is given by

MATH

Example: Let $f(x)=\sin x$, then at $a=\pi /2$ we can compute $f^{\prime }:$

MATH

The tangent line at this point is given by

MATH

or

MATH

We can plot the graph of the function and the tangent line at $x=$ $\pi /2$:

plot $\ \ \ \ \sin x$

on the same graph, plot $y=1$


m150a Lab notes for assign 2__33.png$f(x)=\sin x$, tangent line to $f$ at x=$\frac{\pi }{2}$, $y=1$

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