SOLUTION: using the double angle formula, find the exact value of sin(2x) given sinx=-(5/8) and tan x>0

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Question 929749: using the double angle formula, find the exact value of sin(2x) given sinx=-(5/8) and tan x>0
Answer by lwsshak3(11628) About Me  (Show Source):
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using the double angle formula, find the exact value of sin(2x) given sinx=-(5/8) and tan x>0
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Reference angle x is in quadrant II where sin<0, cos<0
sinx=-5/8
cosx=√(1-sin^2(x))=√(1-(25/64))=√(39/64)=√39/8
sin(2x)=2sinxcosx=2*(-5/8)(√39)/8=-10√39/64