SOLUTION: How do I solve If sin (theta)equals 4/5 , and i need to find cos(theta)

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Question 837112: How do I solve If sin (theta)equals 4/5 , and i need to find cos(theta)
Answer by doodles(24) About Me  (Show Source):
You can put this solution on YOUR website!
Since 4/5 is not a common angle so we have to discover what cos is through Pythagorean theorem. Namely, a%5E2%2Bb%5E2=c%5E2 Furthermore, One needs to remember cos actually equals adjacent/hypotenuse and sin is equal to opposite/hypotenuse. In other words we need to find adjacent because we know opposite = 4 and hypotenuse is = to 5
So:
a%5E2%2B4%5E2=5%5E2 --> a%5E2+=+5%5E2-4%5E2 --> a%5E2=25-16 --> a%5E2=9
--> a+=3
Now that we have adjacent we can get cos.
So adjacent/hypotenuse and cos is equal to 3/5