# Trig

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Use a half-angle identity to find the exact value for sec(x/2) if sinx = -12/13 ; 3pi/2 < x < 2pi

• Trig -

Since sin = -12/13 in QIV, cos = 5/13
sec x/2 = 1/cos(x/2) = √(2/(1+cosx))
= √(1/(1+5/13)) = √(2/(18/13)) = √(26/18) = √13/3

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