Math Problem Statement

if alpha and beta are the distinct roots of acostheta+bsintheta=c then prove that cos (alpha+ beta) = (a²-b²)/(a²+b²)

Solution

We are given the equation acosθ+bsinθ=ca \cos \theta + b \sin \theta = c, and we know that α\alpha and β\beta are the distinct roots of this equation. We are asked to prove that:

cos(α+β)=a2b2a2+b2\cos(\alpha + \beta) = \frac{a^2 - b^2}{a^2 + b^2}

Step 1: Using the sum of angles formula

We know the following

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Roots of Trigonometric Equations
Angle Sum Identities

Formulas

a cos(theta) + b sin(theta) = c
cos(α + β) = cos(α)cos(β) - sin(α)sin(β)

Theorems

Sum of Angles Identity

Suitable Grade Level

Grades 11-12