Question 974438
If tan(x)=5/4 and sin is less than 0, find cos(x). 
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Reference angle x is in quadrant III, where sin<0, cos<0
Hypotenuse of reference right triangle=&#8730;(5^2+4^2)=&#8730;(25+16)=&#8730;41
cos(x)=-4/&#8730;41=-(4&#8730;41)/41