Question

Exact value COS 15 degree

Answer 1

`\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) ) }} \\`

Answer 2

Answer: (√6 + √2)/4

Step-by-step explanation: (√6 + √2)/4