ShmoopTube

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Here's your shmoop du jour...

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cos(A) = 3/7. What is the length of side x?

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And here are your options...

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Okay, so we know the cosine of angle A...

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and we need to use it to find the length of side x...

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The cosine of an angle is equal to the adjacent side over the hypotenuse.

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If the adjacent side is 3 and the hypotenuse is 7, we can use the Pythagorean theorem to

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solve for the missing leg, x.

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So we can just plug our numbers into this formula,

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Three squared plus x squared equals seven squared.

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9 plus x squared equals 49.

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x squared equals 40.

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x equals the square root of 40.

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The square root of 40 is equal to 2 root 10, and there you have it...

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...option C. That's the way to go.

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