Question 952106
if tan&#952; = 4 and 180° < &#952; < 270° determine the exact value of cos&#952
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tan = y/x = 4/1
{{{r = sqrt(x^2 + y^2) = sqrt(17)}}}
|cos| = x/r = {{{sqrt(17)/17}}}
cosine is negative in Q3
--> {{{-sqrt(17)/17}}}