Skip to main content
Ch. R - Algebra Review
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161Not the one you use?Change textbook
Chapter 1, Problem 71a

Determine the largest open intervals of the domain over which each function is (a) increasing See Example 8.

Verified step by step guidance
1
Identify the given function for which you need to determine the intervals of increase. The problem refers to 'each function,' so start by clearly writing down the function(s) involved.
Recall that a function is increasing on intervals where its first derivative is positive. Therefore, find the first derivative of the function, denoted as \(f'(x)\).
Set up the inequality \(f'(x) > 0\) to find where the function is increasing. Solve this inequality to determine the values of \(x\) for which the derivative is positive.
Analyze the critical points where \(f'(x) = 0\) or where \(f'(x)\) is undefined, as these points can mark the boundaries of intervals where the function changes from increasing to decreasing or vice versa.
Combine the results to write the largest open intervals on the domain where \(f'(x) > 0\), which correspond to the intervals where the original function is increasing.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
4m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Domain of a Function

The domain of a function is the set of all input values (usually x-values) for which the function is defined. Identifying the domain is essential before analyzing behavior like increasing or decreasing intervals, especially for trigonometric functions that may have restricted domains due to their definitions or transformations.
Recommended video:
3:43
Finding the Domain of an Equation

Increasing and Decreasing Functions

A function is increasing on an interval if, as the input increases, the output also increases. Formally, f is increasing on an interval if for any x1 < x2 in that interval, f(x1) < f(x2). Understanding this concept helps in determining where the function rises or falls.
Recommended video:
5:57
Graphs of Common Functions

Use of Derivatives to Determine Monotonicity

The derivative of a function indicates its rate of change. If the derivative is positive over an interval, the function is increasing there; if negative, it is decreasing. Calculating and analyzing the derivative is a key method to find the largest intervals where the function is increasing.
Recommended video:
04:42
Solve Trig Equations Using Identity Substitutions