Question

Вычислите: cos(п/3+b)+cos(п/3-b),если cosb=2​

Answer 1

cos(π/3 + b) + cos(π/3 - b) = cosπ/3•cosb - sinπ/3•sinb + cosπ/3•cosb + sinπ/3•sinb = 2cosπ/3•cosb = cosb