SOLUTION: please help me find the exact values of: sin2u given: sinu= -4/5 and pi

SOLUTION: please help me find the exact values of: sin2u given: sinu= -4/5 and pi < u 3pi/2

Question 622497: please help me find the exact values of:
sin2u
given: sinu= -4/5 and pi < u 3pi/2
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
find the exact values of:
sin2u
given: sinu= -4/5 and pi < u 3pi/2
sinu=-4/5 in quadrants III and IV where sin<0
since quadrant IV is not in the domain,(π,3π/2), reference angle is in quadrant III
sinu=-4/5=opposite side/hypotenuse
adjacent side=3 since you are working with a 3-4-5 right triangle
cosu=-3/5 in quadrants III where cos<0
sin 2u=2sinucosu
=2*-4/5*-3/5
=24/25
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