cos^2 A + cos^2 B +/- cos A cos B when A + B is fixed

1. A.
   $\dfrac{1}{4}$
2. B.
   $\dfrac{1}{2}$
3. C.
   $\dfrac{3}{4}$
4. D.
   $1$

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1. A.
   $\dfrac{3}{4}$
2. B.
   $\dfrac{5}{4}$
3. C.
   $\dfrac{-3}{4}$
4. D.
   $\dfrac{-5}{4}$

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1. A.
   $\dfrac{1}{4}$
2. B.
   $\dfrac{3}{4}$
3. C.
   $\dfrac{5}{4}$
4. D.
   $\dfrac{7}{4}$

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