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Grade 11Trigonometry

Find the value of A and B if A>0 and B

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Profile image of Devanshi Gupta
10 Years agoGrade 11
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1 Answer

Profile image of Lab Bhattacharjee
ApprovedApproved Tutor Answer10 Years ago
\text{Using Prosthaphaeresis Formula,} \cos\alpha+\cos\beta=2\cos\dfrac{\alpha+\beta}2\cos\dfrac{\alpha-\beta}2\\ \text{and using Double angle formula, } \cos(\alpha+\beta)=2\cos^2\dfrac{\alpha+\beta}2-1 \\ \text{ form a Quadratic equation in} \cos\dfrac{\alpha+\beta}2 \\ \text{As }\alpha,\beta \text{ are real, the discriminant must be non-negative, but } \\\cos\dfrac{\alpha+\beta}2\le1

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