Let a {\displaystyle {}a} be the minimal positive number fulfilling sin a = cos a {\displaystyle {}\sin a=\cos a} . Compute the area of the surface, which is enclosed by the graph of the cosine function and the graph of the sine function above [ 0 , a ] {\displaystyle {}[0,a]} .
![{\displaystyle {}[0,a]}](https://wikimedia.org/api/rest_v1/media/math/render/svg/78598420acefee80be7601c0fa530cc6c432d7c5)