Aus Online Mathematik Brückenkurs 1

This exercise is somewhat of a trick question, because we don't need any trigonometry to solve it.

Two angles are given in the triangle (the 60° angle and the right-angle) and thus we can use the fact that the sum of all the angles in a triangle is 180°,

\displaystyle v + 60^{\circ} + 90^{\circ} = 180^{\circ}\,,

which gives

\displaystyle v = 180^{\circ} - 60^{\circ} - 90^{\circ} = 30^{\circ}\,\textrm{.}