Evaluate Using the Given Value cos(x) , x=7pi

Replace the variable ${\displaystyle x}$ with ${\displaystyle 7\pi }$ in the expression.

Subtract full rotations of ${\displaystyle 2\pi }$ until the angle is greater than or equal to ${\displaystyle 0}$ and less than ${\displaystyle 2\pi }$.

Apply the reference angle by finding the angle with equivalent trig values in the first quadrant. Make the expression negative because cosine is negative in the second quadrant.

The exact value of ${\displaystyle \cos \left(0\right)}$ is ${\displaystyle 1}$.