Search for: Σa3cos(B−C)=Σa3cos(B−C)=A 3 abcB3 (a+b+c) Cabc (a+ b + c)D0 Register to Get Free Mock Test and Study Material +91 Verify OTP Code (required) I agree to the terms and conditions and privacy policy. Solution:We have,∑a3cos(B−C)=∑k3sin3Acos(B−C)=k3Σsin2Asin(B+C)cos(B−C)=k32Σsin2A(sin2B+sin2C)=k32Σsin2A(sin2B+sin2C)+sin2B(sin2C+sin2A)+sin2C(sin2A+sin2B)=k3Σsin2AsinBcosB+sin2BsinAcosA=k3ΣsinAsinBsin(A+B)=k3[sinAsinBsinC+sinBsinCsinA+sinCsinAsinB]=3(ksinA)(ksinB)(ksinC)=3abcPost navigationPrevious: If 10 sin4α+15cos4α=6 then the value of 27cosec6α+8sec6α is Next: The minimum value of f(x)=sin4x+cos4x, 0≤x≤π2 isRelated content JEE Main 2023 Question Papers with Solutions JEE Main 2024 Syllabus Best Books for JEE Main 2024 JEE Advanced 2024: Exam date, Syllabus, Eligibility Criteria JEE Main 2024: Exam dates, Syllabus, Eligibility Criteria JEE 2024: Exam Date, Syllabus, Eligibility Criteria NCERT Solutions For Class 6 Maths Data Handling Exercise 9.3 JEE Crash Course – JEE Crash Course 2023 NEET Crash Course – NEET Crash Course 2023 JEE Advanced Crash Course – JEE Advanced Crash Course 2023