Mathematics
saruacosta671
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Angle θ is in standard position. If tanθ < 0 and cosθ = -4/5 , find sinθ.

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EchoEdgeman

use the formula, sin^2 x + cos^2 x =1 sin^2 x + (-4/5)^2 = 1 sin^2 x  + 16/25 = 1 sin^2 x = 1-16/25 sin^2 x = (25-16)/25 sin^2 x = 9/25 sin x = +3/5 or -3/5 since both tan and cos are negative, sine will be positive (Quadrant 2). sin x = 3/5.

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