On-line Math 21

3.1  Trigonometric functions

3.1.1  Derivatives of sin(x) and cos(x) .

Example 2 Find (secx)¢.

Solution

Similarly to the previous example,

( sec(x)) ¢ = æ ç è 1 cos(x) ö ÷ ø ¢ = 1¢cos(x)-(cos(x))¢1 cos2(x) = 0·cos(x)-(-sin(x))1 cos2(x) = sin(x) cos2(x) , which is usually written as = sec(x)tan(x).

Copyright (c) 2000 by David L. Johnson.