Question

cosx=-2/5 soo cos 3x =?​

Answer 1

Answer:

46/25

Step-by-step explanation:

Given,

cos(x) = -2/5

Now we know that,

cos(3x) = 4cos³(x) - 3cos(x)

Given the value,

cos(3x) = 4(-2/5)² - 3(-2/5)

cos(3x) = 46/25