Question

cos 2 arccos 5 9

Answer 1

Like this? \(\cos 2 \cdot \arccos (5\cdot 9)\)?

Answer 2

arccos(5/9)

Answer 3

cos2(arccos(5/9))

Answer 4

cos2(arccos(5/9)) or cos²(arccos(5/9))?

Answer 5

cos(2arccos(5/9))

Answer 6

HINT: cos(2x) = cos²(x) - sin²(x) = 2cos²(x) - 1

Answer 7

Let x be \(\arccos \left(\dfrac{5}{9}\right)\).

Another hint: \( \cos(\arccos(a)) = a \) since cos and arccos is inverse of each other, hence cancel each other out.

Does this help you?

Answer 8

?

Answer 9

they want the exact value

Answer 10

You can get exact value using my hints.

Answer 11

Also, remember that cos²b = cos b cos b = (cos b)²

Answer 12

Do you know what to do right now? No?