cos(θ+150°) এর মান?

cos(θ+150°) এর মান নির্ণয়:

আমরা জানি, cos(A+B) = cosA cosB - sinA sinB

সুতরাং, cos(θ+150°) = cosθ cos150° - sinθ sin150°

cos150° = cos(180°-30°) = -cos30° = -\(\frac{\sqrt{3}}{2}\)

sin150° = sin(180°-30°) = sin30° = \(\frac{1}{2}\)

অতএব, cos(θ+150°) = cosθ (-\(\frac{\sqrt{3}}{2}\)) - sinθ (\(\frac{1}{2}\))

cos(θ+150°) = -\(\frac{\sqrt{3}}{2}\)cosθ - \(\frac{1}{2}\)sinθ

cos(θ+150°) = -\(\frac{1}{2}\)(sinθ + \(\sqrt{3}\)cosθ)

সুতরাং, cos(θ+150°) = -1/2(sinθ + \(\sqrt{3}\)cosθ) 🥳