Question

cos²pi/12 + cos²3pi/12 + cos²5pi/12​

Answer 1

_____________________

★ Sᴏʟᴜᴛɪᴏɴ :-

cos²(π/12) + cos²(3π/12) + cos²(5π/12)

Substituting

• π = 180°

➮ cos²(180°/12) + cos²[3(180°)/12] + cos²[5(180°)/12]

➮ cos²(15°) + cos²[3(15°)] + cos²[5(15°)]

➮ cos²(15°) + cos²(45°) + cos²(75°)

➮ 0.96² + (1/√2)² + 0.25²

➮ 0.921 + 1/2 + 0.062

➮ 0.92 + 0.5 + 0.06

➮ cos²(π/12) + cos²(3π/12) + cos²(5π/12) ≈ 1.48

Hence , cos²(π/12) + cos²(3π/12) + cos²(5π/12) ≈ 1.48

_____________________