+280 I know i asked about this already, but is there something im missing, This is the part when i mised class.
+118687 I'll do the first on and you can try the others yourself
\(cos(u)=\frac{\sqrt{15}}{5}\\ cos(2*\frac{u}{2})=\frac{\sqrt{15}}{5}\\ cos^2(\frac{u}{2})-sin^2(\frac{u}{2})=\frac{\sqrt{15}}{5}\\ 1-sin^2(\frac{u}{2})-sin^2(\frac{u}{2})=\frac{\sqrt{15}}{5}\\ 1-2sin^2(\frac{u}{2})=\frac{\sqrt{15}}{5}\\ -2sin^2(\frac{u}{2})=\frac{\sqrt{15}-5}{5}\\ sin^2(\frac{u}{2})=\frac{\sqrt{15}-5}{-10}\\ sin^2(\frac{u}{2})=\frac{5-\sqrt{15}}{10}\\ sin(\frac{u}{2})=\sqrt{\frac{5-\sqrt{15}}{10}}\\ sin(\frac{u}{2})=\frac{\sqrt{(5-\sqrt{15})}}{\sqrt{10}}\times \frac{\sqrt{10}}{\sqrt{10}}\\ sin(\frac{u}{2})=\frac{\sqrt{10(5-\sqrt{15})}}{10}\\ sin(\frac{u}{2})=\frac{\sqrt{50-10\sqrt{15}}}{10}\\ \)
