Aus Online Mathematik Brückenkurs 1

The side marked \displaystyle x is the hypotenuse in the right-angled triangle and the side of length \displaystyle \text{16} is the adjacent to the angle of \displaystyle \text{2}0^{\circ }.

By writing the quotient for \displaystyle \text{cos20}^{\circ }, we obtain the relation

\displaystyle \text{cos20}^{\circ }=\frac{16}{x}

and this gives

\displaystyle x=\frac{16}{\text{cos20}^{\circ }}\quad \left( \approx 17.0 \right).