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Trigonometry!!!!!!!!!!!!!

+2 votes
If the sine of an acute angle is 3/5, what is the cosine of that angle?
asked Feb 16, 2013 in TRIGONOMETRY by andrew Scholar

1 Answer

+2 votes

sine = opposite side of right triangle divided by hypotenuse.

cosine = adjacent side of right triangle divided by hypotenuse.

You were given sinx = 3/5, which tells me that the hypotenuse is 5 and the opposite side is 3.

We use the Pythagorean Theorem from geometry to find the adjacent side.

Let A = adjacent side.

(3)2 + A2 = 52

9 + A2 = 25

Subtract 9 from each side.

A2 = 16

Taking the square root of both sides, we get A = 4.

Like I said before, cosine = adjacent side of right triangle divided by hypotenuse.

Then cosx = 4/5.

answered Feb 16, 2013 by britally Apprentice

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