Ответ:
Объяснение:
cos6x·cos4x – sin6x·sin4x=
=[cos(6x-4x)+cos(6x+4x)/2]-[cos(6x-4x)-cos(6x+4x)/2]=
=(cos2x+cos10x)/2 - cos(2x-cos10x)/2=
=(cos2x+cos10x-cos2x+cos10x)/2=
=2cos10x/2= cos 10x
formuła:
*cosa*cosB=[cos(a-B)+cos(a+B)/2
*sina*sinB=[cos(a-B)-cos(a+b)
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Answers & Comments
Ответ:
Объяснение:
cos6x·cos4x – sin6x·sin4x=
=[cos(6x-4x)+cos(6x+4x)/2]-[cos(6x-4x)-cos(6x+4x)/2]=
=(cos2x+cos10x)/2 - cos(2x-cos10x)/2=
=(cos2x+cos10x-cos2x+cos10x)/2=
=2cos10x/2= cos 10x
formuła:
*cosa*cosB=[cos(a-B)+cos(a+B)/2
*sina*sinB=[cos(a-B)-cos(a+b)