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SMO 2014 Senior Round 1 Question 6

SMO · SMO 2014 Senior Round 1

Question 6

Given that $\tan A=\dfrac{12}5$, $\cos B=-\dfrac35$ and that $A$ and $B$ are in the same quadrant, find the value of $\cos(A-B)$.
  1. $-\frac{63}{65}$
  2. $-\frac{64}{65}$
  3. $\frac{63}{65}$
  4. $\frac{64}{65}$
  5. $\frac{65}{63}$