SOLUTION: if cos t=0.4, with t in quadrant IV, find tan(t+pi)

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Question 850929: if cos t=0.4, with t in quadrant IV, find tan(t+pi)
Answer by lwsshak3(11628) About Me  (Show Source):
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if cos t=0.4, with t in quadrant IV, find tan(t+pi)
cos t=0.4=2/5( In quadrant IV in which cos>0, sin<0, tan<0

tan t=sin/cos=-sqrt%2821%29%2F2
Identity:
tan(t+π)=-√21/2+0/(1-√21/2*0=-√21/2
..
calculator check:
cos t=0.4
t≈293.58˚
t+π≈473.58˚
tan(t+π)≈tan(473.58˚)≈-2.2910
Exact value=-√21/2≈-2.2912