■ No GDC ■Consider an isosceles triangle with the characteristics shown in the figure below where the angle marked \(\theta \) is between the two equal sides of length \(x\), and opposite the side of length \(a\).Find two different methods (ways) to show that \(\cos \left( {\frac{\theta }{2}} \right) = \sqrt {1 - \frac{{{a^2}}}{{4{x^2}}}} \).