Math Problem Statement

if sin theta = x/y then sec theta + cot theta =?

Solution

Given that sinθ=xy\sin \theta = \frac{x}{y}, we need to express secθ+cotθ\sec \theta + \cot \theta in terms of xx and yy.

Step 1: Use the Pythagorean Identity

Since sinθ=xy\sin \theta = \frac{x}{y}, we know: cos2θ+sin2θ=1\cos^2 \theta + \sin^2 \theta = 1 This implies: cosθ=1sin2θ=1(xy)2=y2x2y2=y2x2y\cos \theta = \sqrt{1 - \sin^2 \theta} = \sqrt{1 - \left( \frac{x}{y} \right)^2} = \sqrt{\frac{y^2 - x^2}{y^2}} = \frac{\sqrt{y^2 - x^2}}{y}

Step 2: Express secθ\sec \theta

The secant function is the reciprocal of cosine, so: secθ=1cosθ=yy2x2\sec \theta = \frac{1}{\cos \theta} = \frac{y}{\sqrt{y^2 - x^2}}

Step 3: Express cotθ\cot \theta

The cotangent function is the ratio of cosine to sine, so: cotθ=cosθsinθ=y2x2yxy=y2x2x\cot \theta = \frac{\cos \theta}{\sin \theta} = \frac{\frac{\sqrt{y^2 - x^2}}{y}}{\frac{x}{y}} = \frac{\sqrt{y^2 - x^2}}{x}

Step 4: Add secθ\sec \theta and cotθ\cot \theta

Now, combine the expressions for secθ\sec \theta and cotθ\cot \theta: secθ+cotθ=yy2x2+y2x2x\sec \theta + \cot \theta = \frac{y}{\sqrt{y^2 - x^2}} + \frac{\sqrt{y^2 - x^2}}{x}

This is the simplified expression for secθ+cotθ\sec \theta + \cot \theta in terms of xx and yy.

Would you like further details or have any questions?

Follow-up questions:

  1. How does the Pythagorean identity relate to trigonometric functions?
  2. Can you derive the relationship between secant and cosine?
  3. Why is the cotangent function the ratio of cosine to sine?
  4. Can this expression be simplified further for specific values of xx and yy?
  5. How do trigonometric identities help in solving complex expressions?

Tip:

Understanding the reciprocal identities (secant, cosecant, and cotangent) helps simplify many trigonometric problems quickly.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Reciprocal Trigonometric Functions

Formulas

Pythagorean identity: sin^2(theta) + cos^2(theta) = 1
sec(theta) = 1/cos(theta)
cot(theta) = cos(theta)/sin(theta)

Theorems

Pythagorean Identity

Suitable Grade Level

Grades 10-12