Math Problem Statement

Prove that \(\sqrt{\frac{\sec A - 1}{\sec A + 1}} + \sqrt{\frac{\sec A + 1}{\sec A - 1}} = 2\csc A\).

Solution

To prove the given equation:

secA1secA+1+secA+1secA1=2cscA\sqrt{\frac{\sec A - 1}{\sec A + 1}} + \sqrt{\frac{\sec A + 1}{\sec A - 1}} = 2\csc A

Step-by-Step Proof

  1. Simplify Each Square Root: Let’s consider the terms under the square roots.

    • Rewrite secA\sec A in terms of cosA\cos A: secA=1cosA,secA1=1cosAcosA,secA+1=1+cosAcosA.\sec A = \frac{1}{\cos A}, \quad \therefore \sec A - 1 = \frac{1 - \cos A}{\cos A}, \quad \sec A + 1 = \frac{1 + \cos A}{\cos A}.

    Substituting into the expressions under the square roots:

    secA1secA+1=1cosAcosA1+cosAcosA=1cosA1+cosA.\sqrt{\frac{\sec A - 1}{\sec A + 1}} = \sqrt{\frac{\frac{1 - \cos A}{\cos A}}{\frac{1 + \cos A}{\cos A}}} = \sqrt{\frac{1 - \cos A}{1 + \cos A}}.

    Similarly:

    secA+1secA1=1+cosA1cosA.\sqrt{\frac{\sec A + 1}{\sec A - 1}} = \sqrt{\frac{1 + \cos A}{1 - \cos A}}.

  2. Combine the Two Terms: Substitute the simplified forms back into the equation: 1cosA1+cosA+1+cosA1cosA.\sqrt{\frac{1 - \cos A}{1 + \cos A}} + \sqrt{\frac{1 + \cos A}{1 - \cos A}}.

    Multiply and divide by (1cosA)(1+cosA)\sqrt{(1 - \cos A)(1 + \cos A)} (which simplifies to sin2A\sin^2 A):

    1cosA1+cosA+1+cosA1cosA=(1cosA)(1+cosA)+(1+cosA)(1cosA)sinA.\sqrt{\frac{1 - \cos A}{1 + \cos A}} + \sqrt{\frac{1 + \cos A}{1 - \cos A}} = \frac{\sqrt{(1 - \cos A)(1 + \cos A)} + \sqrt{(1 + \cos A)(1 - \cos A)}}{\sin A}.

    Using the identity 1cos2A=sin2A1 - \cos^2 A = \sin^2 A, the numerator simplifies to:

    sinA+sinAsinA=2.\frac{\sin A + \sin A}{\sin A} = 2.

  3. Express in Terms of cscA\csc A: Since cscA=1sinA\csc A = \frac{1}{\sin A}, the equation simplifies to: 2cscA.2 \csc A.

Thus, the left-hand side equals the right-hand side, proving the equation: secA1secA+1+secA+1secA1=2cscA.\sqrt{\frac{\sec A - 1}{\sec A + 1}} + \sqrt{\frac{\sec A + 1}{\sec A - 1}} = 2 \csc A.


Would you like a deeper explanation for any step? Here are 5 related questions for further exploration:

  1. How is the identity sec2A1=tan2A\sec^2 A - 1 = \tan^2 A derived from trigonometric principles?
  2. Why does 1cosA1+cosA\sqrt{\frac{1 - \cos A}{1 + \cos A}} simplify to sinA\sin A using trigonometric identities?
  3. Can this proof be done graphically or using numerical methods for specific values of AA?
  4. What are some real-world applications of proving trigonometric identities like this one?
  5. How does this equation relate to other trigonometric equations involving cscA\csc A and secA\sec A?

Tip: Practice rewriting trigonometric identities in terms of sine and cosine—it simplifies proofs significantly!

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Math Problem Analysis

Mathematical Concepts

Trigonometric identities
Simplification of expressions

Formulas

\(\sec A = \frac{1}{\cos A}\)
\(1 - \cos^2 A = \sin^2 A\)
\(\csc A = \frac{1}{\sin A}\)

Theorems

Trigonometric Pythagorean identities

Suitable Grade Level

Grades 11-12