Question

cos B + cos (120°+B)+cos(240°+B)+sinB =​

Answer 1

Ответ:

Объяснение:

cosb+cos(180-(60-b))+cos(180+(60+b))+sinb=

=cosb-cos(60-b)-cos(60+b)+sinb=

=cosb+sinb-cos60cosb-sin60sinb-cos60cosb+sin60sinb=

=cosb+sinb-2cosbcos60=cosb+sinb-2*1/2cosb=sinb