Question

I'm not sure at all how to do this
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Answer 1

Explanation:

Cos(Ф) = Adj / Hyp

Cos(Ф) = Adj / 5

use Pythagoras's

`5^(2)` =
`2^(2)` +
`x^(2)`

25 - 4 =
`x^(2)`

21 =
`x^(2)`

`√(21)` = x

Cos(Ф) =
`√(21)` / 5

(using the square root means the answer is exact. so leave it like that.)