(cos^2a*cos^2b+2sina*sinb*cosa*cosb+sin^2a*sin^2b)/cos(a-b) Упростите
cos^2a·cos^2b+2sina·sinb·cosa·cosb+sin^2a·sin^2b= =(cosa*cosb+sina*sinb)^2=cos^2(a-b) (cos^2a·cos^2b+2sina·sinb·cosa·cosb+sin^2a·sin^2b)/cos(a–b)=cos^2(a-b)/cos(a-b)=cos(a-b)