# P.o.t.W. #10

■ 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 $$\cos \left( {\frac{\theta }{2}} \right) = \sqrt {1 - \frac{{{a^2}}}{{4{x^2}}}}$$.

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