SOLUTION: Given cosA = -1/4 and 90 degrees < A < 180 degrees, find tanA in surd form.

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Question 751757: Given cosA = -1/4 and 90 degrees < A < 180 degrees, find tanA in surd form.
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
Given cosA = -1/4 and 90 degrees < A < 180 degrees, find tanA in surd form
sec(A)=1/cos(A)=-4
tan%28A%29=-sqrt%28sec%5E2%28A%29-1%29=-sqrt%2816-1%29=-sqrt%2815%29 (in Q2 where tan<0)
..
Check with calculator:
cos(A)=-1/4
A≈104.4775º
tan(A)=tan(104.4775º)≈-3.873..
Exact value=-√15≈-3.873..