\( \cos ^{2}(x)=\frac{3}{4} \quad z=\cos (x) \)
\( z^{2}=\frac{3}{4} \Rightarrow z=\pm \frac{\sqrt{3}}{2} \)
Rücksubstitution:
\( z=\cos (x) \)
a) \( \cos (x)=\frac{\sqrt{3}}{2} \quad \) b) \( \cos (x)=-\frac{\sqrt{3}}{2} \)
\( x_{1}=\frac{\pi}{6}+2 k π ;k ∈ G \quad \quad x_{3}=\frac{5 \pi}{6}+2k \pi \)
\( x_{2} = \frac{11}{\pi}{6} + 2 k \pi \quad x_{4} = \frac{7 \pi}{6}+2 k π \)