Доказать тождество 2sint*sin2t+cos3t=cost

Question

Доказать тождество

2sint*sin2t+cos3t=cost

Comments

2sint*sin2t+cos3t=cost

Answer 1

Решение во вложении.

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Answer 2

2sint*sin2t+cos(t+2t)=2sint*sin2t+cost*cos2t-sint*sin2t=cost*cos2t+sint*sin2t=cos(t-2t)=
=cos(-t)=cost