【紧急求助】计算:cosα+cos(2π/3 +α)+cos(4π/3 +α)
问题描述:
【紧急求助】计算:cosα+cos(2π/3 +α)+cos(4π/3 +α)
答
=cosα+cos2π/3 *cosα-sin2π/3*sinα+cos4π/3*cosα-sin4π/3* sinα
=cosα-1/2cosα-(根号3)/2sinα-1/2cosα+(根号3)/2sinα
=0