Use ∆abc to find the value of cos a.

Using the catchphrase SohCahToa, we can determine that the cosine ratio is equal to the length of the side adjacent to the angle over the length of the hypotenuse of the right triangle.

To find the cos∠A, we will look for side lengths BC and AB.

cosA =

Since is already in it's simplest form, we can conclude that the cosine of ∠A is .

Hope this helps! :^)

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