Trigonometry
Determine the exact value of the expression without using a calculator.
cos(2arctan8413)\cos\left(2\arctan\frac{84}{13}\right)cos(2arctan1384)
−57929345-\frac{5792}{9345}−93455792
−68877225-\frac{6887}{7225}−72256887
−438509-\frac{438}{509}−509438
618967\frac{618}{967}967618