Determine the exact value of the expression without using a calculator. cos ⁡ ( 2 arctan ⁡ 84 13 ) \cos\left(2\arctan\frac{84}{13}\right) cos ( 2 arctan 13 84 )

− 6887 7225 -\frac{6887}{7225} − 7225 6887

− 5792 9345 -\frac{5792}{9345} − 9345 5792

− 438 509 -\frac{438}{509} − 509 438

618 967 \frac{618}{967} 967 618

11. Inverse Trigonometric Functions and Basic Trig Equations

11. Inverse Trigonometric Functions and Basic Trig Equations / Evaluate Composite Trig Functions / Problem 4

Problem 4

Determine the exact value of the expression without using a calculator.
$\cos\left(2\arctan\frac{84}{13}\right)$

$-\frac{5792}{9345}$

$-\frac{6887}{7225}$

$-\frac{438}{509}$

$\frac{618}{967}$