http://www.matematikk.net/ressurser/mat ... &start=150
[tex]I = \int_{0}^{\pi/2} \sqrt{1 + \cos(x)} \, dx[/tex]
[tex]\cos(ax)^2 + \sin(ax)^2 = 1[/tex]
[tex]\cos(2ax) = \cos(ax)^2- \sin(ax)^2 = 2\cos(ax)^2 -1[/tex]
[tex]\cos\left( \frac{1}{2} x \right) = 2\cos \left( \frac{1}{2}x \right)^2 -1 \Rightarrow \cos(x) + 1 = 2\cos\left(\frac{1}{2}x\right)^2[/tex]
[tex]I = \int_{0}^{\pi/2} \sqrt{2\cos\left(\frac{1}{2}x\right)^2} \, dx[/tex]
[tex]I = \sqrt{2} \int_{0}^{\pi/2} \left| \cos\left( \frac{1}{2}x\right) \right| \, dx[/tex]
[tex]I = \sqrt{2} \left[ 2\sin\left( \frac{1}{2}x\right) \right]_{0}^{\pi/2}[/tex]
[tex]I = \sqrt{2} \left[ 2\sin\left( \frac{\pi}{4}\right) \right][/tex]
[tex]I = \sqrt{2} \cdot 2 \cdot \frac{\sqrt{2}}{2} [/tex]
[tex]I = \int_{0}^{\pi/2} \sqrt{1 + \cos(x)} \, dx = 2[/tex]
[tex]\phantom{hello}[/tex]
![Embarassed :oops:](./images/smilies/icon_redface.gif)