If a = sin^-1(sin(5)) and b = cos^-1(cos(5)), then a^2 + b^2 is equal to

Solution & Explanation

### Related Formula sin^-1(sin x) = x - 2pi text for x in [3pi/2, 5pi/2] cos^-1(cos x) = 2pi - x text for x in [pi, 2pi] ### Core Logic Evaluate a = sin^-1(sin 5): The principal branch of sin^-1 x is [-pi/2, pi/2]. 5 radians is approximately 5 times 57.3^circ approx 286.5^circ (in 4th quadrant). The equivalent angle in the principal domain is 5 - 2pi. Thus, a = 5 - 2pi. Evaluate b = cos^-1(cos 5): The principal branch of cos^-1 x is [0, pi]. 5 radians is in [pi, 2pi]. The equivalent angle is 2pi - 5. Thus, b = 2pi - 5. Calculate a^2 + b^2: a^2 + b^2 = (5 - 2pi)^2 + (2pi - 5)^2 = 2(5 - 2pi)^2 = 2(25 + 4pi^2 - 20pi) = 8pi^2 - 40pi + 50 ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Maths: 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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