Hallo,
\( \int_0^\frac{\pi}{2} \cos^2(x)\,dx + \int_0^\frac{\pi}{2} \sin^2(x)\,dx =\int_0^\frac{\pi}{2} \cos^2(x)+\sin^2(x)\,dx =\int_0^\frac{\pi}{2} 1\,dx = \frac{\pi}{2}\)
und
\( \int_0^\frac{\pi}{4} \sin(x)+\cos(x)\,dx +\int_0^\frac{\pi}{4} \sin(x)\,dx -\int_0^\frac{\pi}{4} \cos(x)\,dx =\int_0^\frac{\pi}{4} 2\sin(x)\,dx = 2 \cdot\int_0^\frac{\pi}{4} \sin(x)\,dx = ...\)
jeweils wegen der Linearität des Integrals