- #1
WK95
- 139
- 1
Homework Statement
Each limit below represents the derivative of some function f at some number a. State such an f and a.
##\lim_{x \rightarrow \pi/4} \frac{tan(x) - 1}{x - \pi/4} ##
Homework Equations
##f'(x) = \lim_{x \rightarrow 0} \frac{f(a + h) - f(a)}{h}##
The Attempt at a Solution
##\lim_{x \rightarrow \frac{\pi}{4}} \frac{tan(x) - 1}{x - \frac{\pi}{4}}##
##\lim_{x \rightarrow \frac{\pi}{4}} \frac{tan(x) - tan(\pi/4)}{x - \frac{\pi}{4}}##
##\lim_{x \rightarrow \frac{\pi}{4}} \frac{tan(\frac{\pi}{4} +(x - \frac{\pi}{4})) - tan(\frac{\pi}{4})}{x - \frac{\pi}{4}}##
##h = x - \frac{\pi}{4}##
##\lim_{x \rightarrow \frac{\pi}{4}} \frac{tan(\frac{\pi}{4} + h) - tan(\frac{\pi}{4})}{h}##
##f(x)=tan(x)##
##a=\frac{\pi}{4}##
The definition of the derivative states that x approaches 0. However, in my approach, i get the answer while h approaches pi/4 so I did something incorrectly with my work. However, the end answer seems to be correct. How do I my work to obey the definition of the derivative to solve the problem?