Core Logic
Let ⁻¹α = A, ⁻¹β = B, ⁻¹γ = C$\sin^{-1}\alpha = A, \sin^{-1}\beta = B, \sin^{-1}\gamma = C$.
Given A + B + C = π$A + B + C = \pi$.
Since A = α, B = β, C = γ$\sin A = \alpha, \sin B = \beta, \sin C = \gamma$, α, β, γ$\alpha, \beta, \gamma$ act like the side lengths of a triangle divided by 2R$2R$ by Sine rule. However, directly dealing with the relation:
(α + β + γ)(α + β - γ) = 3αβ$$(\alpha + \beta + \gamma)(\alpha + \beta - \gamma) = 3\alpha\beta$$
Step 1: Simplify Algebraic Relation
(α + β)² - γ² = 3αβ$$(\alpha + \beta)^2 - \gamma^2 = 3\alpha\beta$$
α² + β² + 2αβ - γ² = 3αβ$$\alpha^2 + \beta^2 + 2\alpha\beta - \gamma^2 = 3\alpha\beta$$
α² + β² - γ² = αβ$$\alpha^2 + \beta^2 - \gamma^2 = \alpha\beta$$
Step 2: Triangle Identification
Divide by 2αβ$2\alpha\beta$:
(α² + β² - γ²)/(2αβ) = (1)/(2)$$\frac{\alpha^2 + \beta^2 - \gamma^2}{2\alpha\beta} = \frac{1}{2}$$
By Cosine Rule, C = (1)/(2)$\cos C = \frac{1}{2}$.
Since C = ⁻¹γ$C = \sin^{-1}\gamma$, we know C = γ$\sin C = \gamma$.
C = √(1 - γ²) = (1)/(2)$\cos C = \sqrt{1 - \gamma^2} = \frac{1}{2}$.
Step 3: Final Solution
1 - γ² = (1)/(4) γ² = (3)/(4)$$1 - \gamma^2 = \frac{1}{4} \implies \gamma^2 = \frac{3}{4}$$
Since C$C$ is an angle of a triangle (or sum equals π$\pi$ and elements are positive limits), γ = C > 0$\gamma = \sin C > 0$.
γ = √(3)2$$\gamma = \frac{\sqrt{3}}{2}$$
Pattern Recognition
The expression (α + β + γ)(α + β - γ) = 3αβ$(\alpha + \beta + \gamma)(\alpha + \beta - \gamma) = 3\alpha\beta$ perfectly mirrors the Cosine Rule standard form giving C = 1/2$\cos C = 1/2$.
Chapter Mix
Class 12 Maths: Inverse Trigonometric Functions
Class 11 Maths: Trigonometric Functions