What is Exact trigonometric values?

In mathematics, the values of the trigonometric functions can be expressed approximately, as in cos ⁡ ≈ 0.707 {\displaystyle \cos\approx 0.707} , or exactly, as in cos ⁡ = 2 / 2 {\displaystyle \cos={\sqrt {2}}/2}. While trigonometric tables contain many approximate values, the exact values for certain angles can be expressed by a combination of arithmetic operations and square roots.