SOLUTION: If sin 0 = 4/5, what is the value of cos 0 in quadrant 1?

Question 824976: If sin 0 = 4/5, what is the value of cos 0 in quadrant 1?

Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
If sin(theta) = 4/5, what is the value of cos(theta) in quadrant 1?

sin^2(theta) + cos^2(theta) = 1

(4/5)^2 + cos^2(theta) = 1

16/25 + cos^2(theta) = 1

cos^2(theta) = 1 - 16/25

cos^2(theta) = 25/25 - 16/25

cos^2(theta) = (25 - 16)25

cos^2(theta) = 9/25

cos(theta) = sqrt(9/25) ... we are in quadrant I, so cos(theta) > 0

cos(theta) = 3/5
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