Math Problem Statement

csc(-x)/sec(-x)=-cotx

Solution

We are tasked with simplifying the expression csc(x)sec(x)\frac{\csc(-x)}{\sec(-x)} and verifying that it equals cot(x)-\cot(x).

Step 1: Use the properties of trigonometric functions

We know the following identities for negative angles:

  • csc(x)=csc(x)\csc(-x) = -\csc(x) because csc(x)=1sin(x)\csc(x) = \frac{1}{\sin(x)}, and sin(x)=sin(x)\sin(-x) = -\sin(x).
  • sec(x)=sec(x)\sec(-x) = \sec(x) because sec(x)=1cos(x)\sec(x) = \frac{1}{\cos(x)}, and cos(x)=cos(x)\cos(-x) = \cos(x).

Thus, we can rewrite the expression as: csc(x)sec(x)=csc(x)sec(x)\frac{\csc(-x)}{\sec(-x)} = \frac{-\csc(x)}{\sec(x)}

Step 2: Express csc(x)\csc(x) and sec(x)\sec(x) in terms of sin(x)\sin(x) and cos(x)\cos(x)

Using the definitions of csc(x)\csc(x) and sec(x)\sec(x), we have: csc(x)sec(x)=1sin(x)1cos(x)=cos(x)sin(x)\frac{-\csc(x)}{\sec(x)} = \frac{-\frac{1}{\sin(x)}}{\frac{1}{\cos(x)}} = -\frac{\cos(x)}{\sin(x)}

Step 3: Recognize the resulting expression

The expression cos(x)sin(x)-\frac{\cos(x)}{\sin(x)} is the definition of cot(x)-\cot(x), because: cot(x)=cos(x)sin(x)\cot(x) = \frac{\cos(x)}{\sin(x)} Therefore: cos(x)sin(x)=cot(x)-\frac{\cos(x)}{\sin(x)} = -\cot(x)

Final Result:

csc(x)sec(x)=cot(x)\frac{\csc(-x)}{\sec(-x)} = -\cot(x) This confirms the identity is true.


Would you like further clarification or have any additional questions on this topic?

Related Questions:

  1. What is the proof of the identity csc(x)=1sin(x)\csc(x) = \frac{1}{\sin(x)}?
  2. How does the property cos(x)=cos(x)\cos(-x) = \cos(x) relate to even functions in trigonometry?
  3. What is the relationship between cot(x)\cot(x) and other trigonometric functions like tan(x)\tan(x)?
  4. How would you simplify sec(x)csc(x)\frac{\sec(x)}{\csc(x)}?
  5. What are the properties of even and odd functions in trigonometry?

Tip: When working with trigonometric identities involving negative angles, remember the key rules that sin(x)=sin(x)\sin(-x) = -\sin(x) (odd function) and cos(x)=cos(x)\cos(-x) = \cos(x) (even function). These can help simplify most expressions.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Negative Angle Identities
Trigonometric Functions

Formulas

csc(x) = 1/sin(x)
sec(x) = 1/cos(x)
cot(x) = cos(x)/sin(x)
csc(-x) = -csc(x)
sec(-x) = sec(x)

Theorems

Even-Odd Function Theorem
Negative Angle Identities

Suitable Grade Level

Grades 10-12