Respuesta :

blackshades
Answer:
- 0.944

Step-by-step explanation:
We know that,
cos 3A = 4 cos³A - 3 cos A (formula)

So,
If cos A = 0.4,

cos 3A = 4 cos³A - 3 cos A
cos 3A = 4 × (0.4)³ - 3 × (0.4)
cos 3A = 4 × 0.064 - 1.2
cos 3A = - 0.944


Hope it helps ⚜




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