Question

-47 cos 2a, если cos a = -0,4

Answer 1

Ответ:

31,96

Пошаговое объяснение:

-47(2cos²a - 1) = 47 - 94cos²a = 47 - 94*0,16 = 47 - 15,04 = 31,96

Answer 2

To find the value of -47 cos 2a when cos a = -0.4, we need to use the double-angle identity for cosine, which states:

cos 2a = 2 * cos^2(a) - 1

Given that cos a = -0.4, we can substitute this value into the identity:

cos 2a = 2 * (-0.4)^2 - 1

Now, let's calculate the value:

cos 2a = 2 * (0.16) - 1 cos 2a = 0.32 - 1 cos 2a = -0.68

Finally, we can find the value of -47 cos 2a:

-47 * cos 2a = -47 * (-0.68) = 31.96

So, when cos a = -0.4, the value of -47 cos 2a is approximately 31.96.