Chapter 1: Problem 17
\(\sec 45^{\circ}\)
Short Answer
Expert verified
\(\sec 45^{\circ} = \sqrt{2}\)
Step by step solution
01
Understanding the Function
The cosecant function, also known as secant, is the reciprocal of the cosine function. To find \( \sec 45^{\circ} \), we first need the value of \( \cos 45^{\circ} \).
02
Finding \(\cos 45^{\circ}\)
To find \(\cos 45^{\circ}\), we refer to the unit circle or standard trigonometric values. We know that \(\cos 45^{\circ} = \frac{1}{\sqrt{2}}\).
03
Reciprocal to Find \(\sec 45^{\circ}\)
Now that we know \(\cos 45^{\circ} = \frac{1}{\sqrt{2}}\), we take the reciprocal to find \(\sec 45^{\circ}\). This gives us \(\sec 45^{\circ} = \frac{1}{\frac{1}{\sqrt{2}}} = \sqrt{2}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Trigonometric Functions
Trigonometric functions are essential mathematical functions that relate the angles of a triangle to the lengths of its sides. They are usually defined for right-angled triangles and include sine, cosine, tangent, as well as their reciprocals: cosecant, secant, and cotangent. These functions help us understand the relationships between angles and side lengths.
In a right triangle,
In a right triangle,
- Sine ( \( \sin \theta \) ): The ratio of the opposite side to the hypotenuse.
- Cosine ( \( \cos \theta \) ): The ratio of the adjacent side to the hypotenuse.
- Tangent ( \( \tan \theta \) ): The ratio of the opposite side to the adjacent side.
- Secant ( \( \sec \theta \) ): The reciprocal of cosine, or \( \frac{1}{\cos \theta} \).
Unit Circle
The unit circle is a fundamental concept in trigonometry, representing a circle with a radius of 1 centered at the origin (0,0) on the coordinate plane. This simple yet powerful tool helps us visualize and understand trigonometric functions across different angles. When dealing with the unit circle,
- The x-coordinate of a point on the unit circle corresponds to the cosine of the angle.
- The y-coordinate corresponds to the sine of the angle.
- It allows us to define trigonometric functions for all real numbers, not just within a triangle.
Reciprocal Identities
Reciprocal identities are important in trigonometry, providing relationships between the main trigonometric functions and their reciprocals. These identities help simplify calculations and support the understanding of trigonometric behaviour.
- Secant as a Reciprocal: Since secant is the reciprocal of cosine, \( \sec \theta = \frac{1}{\cos \theta} \). This identity is used when calculating \( \sec 45^{\circ} \). Knowing \( \cos 45^{\circ} = \frac{1}{\sqrt{2}} \), the \( \sec 45^{\circ} = \sqrt{2} \).
- Other Reciprocals: The other primary reciprocal identities are cosecant, \( \csc \theta = \frac{1}{\sin \theta} \), and cotangent, \( \cot \theta = \frac{1}{\tan \theta} \).