If alpha>beta>gamma>0 then the expression cot^-1left\beta+frac(1+beta^2)(alpha-beta)right\+cot^-1left\gamma+frac(1+gamma^2)(beta-gamma)right\+cot^-1left\alpha+frac(1+alpha^2)(gamma-alpha)right\ is equal to: [cite: 3257, 3258]

Solution & Explanation

### Related Formula The standard conversion between cot^-1(x) and tan^-1(x) depends on the sign of x: cot^-1(x) = tan^-1left(frac1xright) quad textif x > 0 cot^-1(x) = pi + tan^-1left(frac1xright) quad textif x < 0 ### Core Logic Simplify the interior terms algebraic representations: beta + frac1+beta^2alpha-beta = fracalphabeta - beta^2 + 1 + beta^2alpha-beta = frac1+alphabetaalpha-beta gamma + frac1+gamma^2beta-gamma = fracbetagamma - gamma^2 + 1 + gamma^2beta-gamma = frac1+betagammabeta-gamma alpha + frac1+alpha^2gamma-alpha = fracalphagamma - alpha^2 + 1 + alpha^2gamma-alpha = frac1+alphagammagamma-alpha ### Step 1: Convert to Inverse Tangent terms Since alpha > beta > gamma > 0: 1. frac1+alphabetaalpha-beta > 0 Rightarrow cot^-1left(frac1+alphabetaalpha-betaright) = tan^-1left(fracalpha-beta1+alphabetaright) 2. frac1+betagammabeta-gamma > 0 Rightarrow cot^-1left(frac1+betagammabeta-gammaright) = tan^-1left(fracbeta-gamma1+betagammaright) 3. frac1+alphagammagamma-alpha < 0 (since gamma - alpha < 0) Rightarrow cot^-1left(frac1+alphagammagamma-alpharight) = pi + tan^-1left(fracgamma-alpha1+alphagammaright) ### Step 2: Telescopic Sum Evaluation Apply the difference identity for arctan, tan^-1left(fracx-y1+xyright) = tan^-1x - tan^-1y : = (tan^-1alpha - tan^-1beta) + (tan^-1beta - tan^-1gamma) + pi + (tan^-1gamma - tan^-1alpha) All variables cancel symmetrically leaving[cite: 3886, 3887]: = pi ### Pattern Recognition The sign trap is the most vital component of this question. The ordering alpha > beta > gamma > 0 means the last term contains a denominator with a negative difference (gamma - alpha), introducing the +pi offset according to the principal range of cot^-1(x). ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Inverse Trigonometric Functions

Reference Study Guides

More Inverse Trigonometric Functions Previous-Year Questions — Page 3

Q15 jee_main_2024_31_jan_morning Properties of Inverse Trigonometric Functions
For alpha, beta, gamma neq 0. If sin^-1alpha + sin^-1beta + sin^-1gamma = pi and (alpha + beta + gamma)(alpha - gamma + beta) = 3 alphabeta then gamma equal to
  • A. fracsqrt32
  • B. frac1sqrt2
  • C. fracsqrt3 - 12sqrt2
  • D. sqrt3

Solution

### Core Logic Let sin^-1alpha = A, sin^-1beta = B, sin^-1gamma = C. Given A + B + C = pi. Since sin A = alpha, sin B = beta, sin C = gamma, alpha, beta, gamma act like the side lengths of a triangle divided by 2R by Sine rule. However, directly dealing with the relation: (alpha + beta + gamma)(alpha + beta - gamma) = 3alphabeta ### Step 1: Simplify Algebraic Relation (alpha + beta)^2 - gamma^2 = 3alphabeta alpha^2 + beta^2 + 2alphabeta - gamma^2 = 3alphabeta alpha^2 + beta^2 - gamma^2 = alphabeta ### Step 2: Triangle Identification Divide by 2alphabeta: fracalpha^2 + beta^2 - gamma^22alphabeta = frac12 By Cosine Rule, cos C = frac12. Since C = sin^-1gamma, we know sin C = gamma. cos C = sqrt1 - gamma^2 = frac12. ### Step 3: Final Solution 1 - gamma^2 = frac14 implies gamma^2 = frac34 Since C is an angle of a triangle (or sum equals pi and elements are positive limits), gamma = sin C > 0. gamma = fracsqrt32 ### Pattern Recognition The expression (alpha + beta + gamma)(alpha + beta - gamma) = 3alphabeta perfectly mirrors the Cosine Rule standard form giving cos C = 1/2. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Maths: Inverse Trigonometric Functions Class 11 Maths: Trigonometric Functions

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