Question 622024: please help me find the exact value of
tan2u
given: sinu= -4/5 & pi < u < 3pi/2
Answer by lwsshak3(11628)   (Show Source):
You can put this solution on YOUR website! find the exact value of
tan2u
given: sinu= -4/5 & 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
tanu=opposite side/adjacent side=4/3 in quadrant III where tan>0
tan2u=2tanu/(1-tan^2u)=2*4/3/(1-(4/3)^2)=(8/3)/(1-16/9)=(8/3)/(-7/9)=-72/21
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