Math Problem Statement

Simplify the expression \(\frac{1 - \cos x}{\sin x} + \frac{\sin x}{1 - \cos x}\) and determine its value.

Solution

To solve the problem given in the image, we simplify the expression:

1cosxsinx+sinx1cosx\frac{1 - \cos x}{\sin x} + \frac{\sin x}{1 - \cos x}

Step 1: Find a common denominator

The common denominator between the two fractions is (sinx)(1cosx)(\sin x)(1 - \cos x). Rewrite each fraction with this common denominator:

1cosxsinx=(1cosx)2sinx(1cosx)\frac{1 - \cos x}{\sin x} = \frac{(1 - \cos x)^2}{\sin x (1 - \cos x)}

sinx1cosx=sin2xsinx(1cosx)\frac{\sin x}{1 - \cos x} = \frac{\sin^2 x}{\sin x (1 - \cos x)}

Now, the expression becomes:

(1cosx)2+sin2xsinx(1cosx)\frac{(1 - \cos x)^2 + \sin^2 x}{\sin x (1 - \cos x)}

Step 2: Simplify the numerator

Expand (1cosx)2(1 - \cos x)^2:

(1cosx)2=12cosx+cos2x(1 - \cos x)^2 = 1 - 2\cos x + \cos^2 x

So the numerator is:

12cosx+cos2x+sin2x1 - 2\cos x + \cos^2 x + \sin^2 x

Using the Pythagorean identity sin2x+cos2x=1\sin^2 x + \cos^2 x = 1, substitute 11 for sin2x+cos2x\sin^2 x + \cos^2 x:

12cosx+1=22cosx1 - 2\cos x + 1 = 2 - 2\cos x

Thus, the expression becomes:

22cosxsinx(1cosx)\frac{2 - 2\cos x}{\sin x (1 - \cos x)}

Step 3: Factorize the numerator

Factor 22 from the numerator:

2(1cosx)sinx(1cosx)\frac{2(1 - \cos x)}{\sin x (1 - \cos x)}

Cancel 1cosx1 - \cos x from the numerator and denominator (provided 1cosx01 - \cos x \neq 0):

2sinx\frac{2}{\sin x}

Step 4: Simplify using reciprocal identities

The reciprocal of sinx\sin x is cscx\csc x. Thus, the result is:

2cscx2 \csc x

Final Answer:

The correct option is A. 2cscx2 \csc x.

Would you like further clarifications or detailed steps? Here are some related questions:

  1. What are the Pythagorean identities in trigonometry?
  2. How does factoring simplify trigonometric expressions?
  3. When is it valid to cancel terms in a fraction?
  4. What are the reciprocal trigonometric functions?
  5. Can this method be applied to different trigonometric equations?

Tip: Always look for opportunities to use trigonometric identities to simplify expressions efficiently.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Simplification of Trigonometric Expressions
Reciprocal Identities

Formulas

Pythagorean identity: \(\sin^2 x + \cos^2 x = 1\)
Reciprocal identity: \(\csc x = \frac{1}{\sin x}\)

Theorems

Basic Trigonometric Identities

Suitable Grade Level

Grades 10-12