# Do I Need A Trigonometric Table?

Geometry Level 1

$\large \cos \dfrac\pi2, \quad \cos \dfrac{2\pi}3, \quad \cos\dfrac{3\pi}4, \quad \cos\dfrac{4\pi}5$

All of the above 4 numbers are negative except $\text{\_\_\_\_\_\_\_\_\_\_}$.

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