Problem 6 - A Graphical Approach to Precalculus with Limits

Question

Fill in the blank(s) to complete each fundamental identity. \(\frac{\sin x}{\cos x}=\) _______

Step-by-Step Solution

Answer

\( \frac{\sin x}{\cos x} = \tan x \)

Step 1: Recognize the Trigonometric Identity

The given expression \( \frac{\sin x}{\cos x} \) is a well-known trigonometric identity. This expression represents one of the fundamental trigonometric functions.

Step 2: Identify the Equivalent Trigonometric Function

The expression \( \frac{\sin x}{\cos x} \) can be identified as \( \tan x \). This is one of the basic identities in trigonometry, where tangent of an angle is defined as the ratio of the sine to the cosine of that angle.

Step 3: Write the Complete Identity

Using the identity from Step 2, we complete the expression: \( \frac{\sin x}{\cos x} = \tan x \). This shows the equivalence between the two expressions.

Key Concepts

Tangent Function

The tangent function, commonly written as \( \tan x \), is one of the primary trigonometric functions. It describes the ratio of the opposite side to the adjacent side in a right triangle. This makes it an essential tool in solving a variety of geometric and trigonometric problems.

Mathematically, it can be expressed using the sine function and the cosine function:

• \( \tan x = \frac{\sin x}{\cos x} \)

The tangent function is periodic, meaning it repeats its values at regular intervals. Its period is \( \pi \) radians or 180 degrees. This means that \( \tan(x + \pi) = \tan x \).
The graph of the tangent function exhibits vertical asymptotes at odd multiples of \( \frac{\pi}{2} \), where the cosine function equals zero, causing the function to be undefined. Understanding the tangent function and its properties helps in navigating complex trigonometric problems with more precision.

Sine Function

The sine function, denoted as \( \sin x \), is another fundamental trigonometric function. It represents the ratio of the length of the opposite side to the length of the hypotenuse in a right triangle. As one of the building blocks of trigonometry, understanding the sine function is necessary for mastering the subject.

Some critical characteristics of the sine function include:

• Its range is from -1 to 1.
• It is an odd function, which means \( \sin(-x) = -\sin(x) \).
• The function is periodic with a period of \( 2\pi \) radians or 360 degrees, meaning \( \sin(x + 2\pi) = \sin x \).

Additionally, the graph of the sine function is a continuous, smooth wave, often referred to as a sinusoidal wave. This functionality is vital in various real-world applications such as sound waves, light waves, and other phenomena that exhibit periodic behavior.

Cosine Function

The cosine function, written as \( \cos x \), is closely related to the sine function. It measures the ratio of the adjacent side to the hypotenuse in a right triangle. As with the sine function, it forms a basis for understanding more complex trigonometric and mathematical concepts.

Characteristics of the cosine function include:

• Its range is also from -1 to 1.
• It is an even function, indicated by the property \( \cos(-x) = \cos x \).
• The period of the cosine function is \( 2\pi \) radians or 360 degrees, so \( \cos(x + 2\pi) = \cos x \).

The cosine graph, like the sine graph, is sinusoidal but starts at its maximum value when \( x = 0 \). This function is immensely useful in analyzing alternating currents, waves, and oscillatory systems. Understanding both sine and cosine functions allows individuals to master their applications in diverse fields, enhancing problem-solving skills effectively.