(Cos4A-cos2A)/sin3A*sinA=-2 help me

Question

(Cos4A-cos2A)/sin3A*sinA=-2 help me

Answer 1

-2sin[(4a-2a)/2]*sin[(4a+2a)/2]/(sin3a*sina)=-2sina*sin3a/(sin3a*sina)=-2
-2=-2

Answer 2

Решение во вложении.

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