Упростите cos(a-b)-cosa*cosb

Решение 1) sin(a+B)-cos(a-B) = sinacosB+ cosasinB - cosacosB - sinasinB = (sinacosB- sinasinB )+ (cosasinB - cosacosB) = sina(cosB -sinB) +cosa(sinB - cosB) = = sina(cosB -sinB) - cosa(cosB- sinB ) = (cosB -sinB) ( sina - cosa) 2) cos(a+B)-sin(a-B) = cosacosB - sinasinB- sinacosB+ cosasinB = = (cosacosB + cosasinB) - (sinasinB + sinacosB) = cosa(cosB + sinB) - sina(sinB + cosB) = = (cosB + sinB)( cosa -sina) 3) (cosB -sinB) ( sina - cosa)/ (cosB + sinB)( cosa -sina) = (sinB -cosB)/ ( sinB+ cosB )