Considering the principal values of the inverse trigonometric functions, sin^-1left(fracsqrt32 x + frac12sqrt1 - x^2right), where -frac12 < x < frac1sqrt2, is equal to

Solution & Explanation

### Related Formula Trigonometric Sine Identity: sin(A + B) = sin A cos B + cos A sin B ### Core Logic Let sin^-1x = theta implies x = sintheta and sqrt1-x^2 = costheta. Given constraint -frac12 < x < frac1sqrt2 implies -fracpi6 < theta < fracpi4. Substitute parameter representations into expression: sin^-1left(fracsqrt32sintheta + frac12costhetaright) = sin^-1left(sinthetacosfracpi6 + costhetasinfracpi6right) sin^-1left(sinleft(theta + fracpi6right)right) ### Step 1: Check Principal Bounds Evaluate bounds for arguments: since -fracpi6 < theta < fracpi4: -fracpi6 + fracpi6 < theta + fracpi6 < fracpi4 + fracpi6 implies 0 < theta + fracpi6 < frac5pi12 This lies completely within the principal value branch of sin^-1x, which is left[-fracpi2, fracpi2right]. Therefore, sin^-1left(sinleft(theta + fracpi6right)right) = theta + fracpi6. ### Step 2: Final Form Substituting back theta = sin^-1x: fracpi6 + sin^-1x ### Pattern Recognition Always check primary interval bounds when stripping inverse operators. If the arguments exceed bounds, quadrant mapping transformations must be performed. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Inverse Trigonometric Functions

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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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