SOLUTION: Use trig identities and the given information to determine the exact value Secx= -8/5, pi <or equal to X <or equal to 3pi/2, find cosx

Algebra ->  Trigonometry-basics -> SOLUTION: Use trig identities and the given information to determine the exact value Secx= -8/5, pi <or equal to X <or equal to 3pi/2, find cosx      Log On


   

Question 1022071: Use trig identities and the given information to determine the exact value
Secx= -8/5, pi
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!

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Use trig identities and the given information to determine the exact value
Secx= -8/5, pi <= X <= 3pi/2, find cosx
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By definition, sec = r/x
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Since X is in QIII, x is negative::
Therefore: r = 8 and x = -5
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Then cos(x) = x/r = 1/sec(x) = 1/(-8/5) = -5/8
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Cheers,
Stan H.
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