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Exact value COS 15 degree

User Ylangylang
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2 Answers

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\purple{\frak{ \implies cos 15\degree = cos(60° - 45°) }}\\


\sf \implies cos(60° - 45°) = cos (60). cos45° + sin60° . sin45° \\


\pink{\frak{\because cos(A-B) = cos A. cos B + sin A. sin B}}\\


\sf \implies cos(60° - 45°) = (1)/(2) * (1)/( √(2) ) + ( √(3) )/(2) * (1)/( √(2) ) \\


\sf \implies cos(60° - 45°) = (1)/( 2√(2) ) + ( √(3) )/(2 √(2) ) \\


\sf \implies { \cos(60° - 45°) = (1 + √(3) )/( 2√(2) )} \\


\sf \implies \purple{ \frak{ \cos15° = (1 + √(3) )/( 2√(2) ) }} \\

User Kalu
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6.4k points
3 votes

Answer: (√6 + √2)/4

Step-by-step explanation: (√6 + √2)/4

User Rheone
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6.8k points